How to Measure Aluminium Windows and Doors

How to Measure Aluminium Windows and Doors

Knowing how to measure aluminium windows and doors is important when requesting a quotation, planning a renovation or preparing to order custom-made products.

For preliminary pricing, basic width and height measurements are often enough to begin.

For manufacture, however, the dimensions must be accurate and appropriate for the actual installation method.

This is especially important with replacement windows and doors because existing openings may be:

  • Out of square
  • Out of level
  • Out of plumb
  • Different internally and externally
  • Concealed by trims or reveals
  • Affected by brickwork, render or cladding

The purpose of measuring is not simply to find the largest visible width and height.

It is to understand the opening that the new aluminium window or door must actually fit.

How Do You Measure an Aluminium Window?

Measure the opening width at several points, measure the height at several points, check the diagonals and record the smallest relevant dimensions for the proposed installation method.

For a preliminary quote, record:

  • Width
  • Height
  • Window type
  • Opening direction
  • Approximate reveal depth
  • Photos
  • Project location

For manufacturing, the final dimensions should be verified according to the agreed installation method.

What Tools Do You Need?

Useful measuring tools include:

  • Tape measure
  • Laser measure where appropriate
  • Spirit level
  • Pencil
  • Notepad
  • Phone or camera
  • Straight edge

For larger openings, two people can make measuring easier and more reliable.

Measure in Millimetres

Aluminium windows and doors are generally easiest to quote and manufacture using millimetres.

For example:

1200 mm wide × 1500 mm high

Using millimetres reduces ambiguity and provides the level of detail needed for custom manufacture.

Always Record Width First

A clear convention helps avoid mistakes.

Record dimensions as:

Width × Height

For example:

1800 W × 2100 H

Do not send two numbers without identifying which is width and which is height.

Measuring Window Width

Measure the width at more than one location.

For example:

  • Near the top
  • Across the middle
  • Near the bottom

Existing openings are not always perfectly parallel.

If the measurements differ, record them rather than assuming the opening is square.

Measuring Window Height

Measure the height at several locations.

For example:

  • Left side
  • Centre
  • Right side

Again, record any differences.

This can help identify whether the sill or head is out of level.

Why Take Multiple Measurements?

Older buildings can move over time.

Brickwork, framing and other construction can also vary slightly during installation.

A single measurement can therefore miss an important variation.

Multiple measurements help establish the actual shape of the opening.

Measure the Diagonals

Diagonal measurements help determine whether the opening is square.

Measure:

  • Top-left corner to bottom-right corner
  • Top-right corner to bottom-left corner

If the dimensions are similar, the opening is likely relatively square.

If they differ substantially, the opening may be out of square.

Why Does Squareness Matter?

A rectangular aluminium window cannot automatically compensate for a badly distorted opening.

An out-of-square opening can result in:

  • Uneven installation gaps
  • Difficult fixing
  • Poor appearance
  • Problems with operation

The condition should be understood before manufacture.

Check Whether the Opening Is Level

Check the sill or base of the opening with a level where possible.

This is especially important for doors.

An out-of-level threshold can affect:

  • Door operation
  • Drainage
  • Installation clearance
  • Finished appearance

Check Whether the Opening Is Plumb

Vertical sides should also be checked.

If a jamb is significantly out of plumb, this may affect the new frame size or surrounding building work.

Rough Opening vs Finished Opening

These are not always the same thing.

A rough opening is the structural opening before final finishes.

A finished opening may include:

  • Plaster
  • Render
  • Timber reveals
  • Trims
  • Cladding

You need to know which dimension the new window is intended to suit.

Window Opening Size vs Window Frame Size

The manufactured aluminium frame is typically not simply made exactly the same size as the building opening.

Installation clearance is generally required.

The appropriate clearance depends on:

  • Window system
  • Construction type
  • Installation method
  • Flashing
  • Sealant requirements

Final manufacturing dimensions should therefore be based on the actual installation strategy.

Do Not Automatically Deduct a Fixed Amount

A common mistake is assuming that a universal deduction can be made from every opening.

For example, simply deducting the same number of millimetres from every measurement may not suit every project.

Required clearance depends on the construction and installation method.

Measuring New-Build Windows

For new construction, window sizes may be taken from:

  • Architectural drawings
  • Window schedules
  • Framing dimensions
  • Site measurements

Before manufacture, drawings and actual construction should be coordinated.

Do not assume the built opening exactly matches the plan without verification where final site dimensions are required.

Measuring Replacement Windows

Replacement windows require particular care because part of the existing frame or opening may be concealed.

Record:

  • Existing window width
  • Existing window height
  • Visible frame dimensions
  • Internal reveal dimensions
  • External opening dimensions
  • Photos inside and outside

The intended replacement method must be established before final sizing.

Measuring Timber Windows for Aluminium Replacement

When replacing timber windows, determine whether the new aluminium window will:

  • Replace the entire timber frame
  • Fit within part of the existing frame
  • Use existing reveals
  • Require new reveals

These methods can produce very different manufacturing dimensions.

Measuring Existing Aluminium Windows for Replacement

Do not assume the visible aluminium frame dimension is automatically the new manufacturing size.

Check:

  • External frame
  • Internal reveals
  • Brick or cladding opening
  • Existing fixing method
  • Trims

The replacement methodology should determine the final dimension.

Measuring Steel Windows for Aluminium Replacement

Older steel windows may be embedded into masonry or other building materials.

Before ordering a replacement, understand:

  • What will be removed
  • What will remain
  • Actual opening dimensions after removal
  • Required making good

This may require more investigation than a simple surface measurement.

Measuring Windows in Brickwork

Brick openings can be misleading because the visible brick size may differ from the internal opening.

Measure where accessible:

  • External brick opening
  • Existing frame
  • Internal reveal

Also photograph:

  • Head
  • Sill
  • Both jambs

Measuring Windows in Weatherboard Walls

Weatherboard and lightweight cladding can sometimes conceal parts of the window flange or flashing.

The installation method should be understood before final dimensions are confirmed.

Measuring Windows in Rendered Walls

Render can reduce or obscure the original opening.

Measure carefully and note whether the render finishes:

  • Against the frame
  • Over a flange
  • Over a trim

Removal can expose a larger underlying opening.

Measuring Windows With Timber Reveals

Record the reveal depth as well as the window width and height.

This can help coordinate the new frame with the internal wall thickness.

What Is Reveal Depth?

Reveal depth is the distance through the wall or reveal area associated with the window installation.

It can affect:

  • Internal finish
  • Window position
  • Trims
  • Installation detail

Measuring a Fixed Aluminium Window

For a fixed window, record:

  • Overall opening width
  • Overall opening height
  • Required glass or frame divisions
  • Mullion positions
  • Transom positions

If the architectural layout is important, provide drawings or photos showing the intended proportions.

Measuring an Awning Window

In addition to width and height, consider:

  • External opening clearance
  • Window shrouds
  • Eaves
  • Screens
  • Adjacent structures

An awning sash needs sufficient space to open outward.

Measuring a Sliding Window

Record:

  • Width
  • Height
  • Desired sliding direction
  • Number of panels
  • Flyscreen requirement

Identify which side should open when viewed from the relevant side.

Always Clarify Opening Direction

Terms such as left and right can become confusing.

Where possible, mark the opening direction on:

  • Drawing
  • Photo
  • Window schedule

This reduces interpretation errors.

Measuring Sashless Windows

Sashless systems can have different dimensional requirements from conventional aluminium windows.

Provide the overall opening dimensions and desired configuration so the system can be assessed.

Measuring Aluminium Doors

Doors require the same basic width and height measurements as windows but need additional attention to:

  • Threshold
  • Floor level
  • Paving
  • Step-down
  • Opening direction
  • Panel configuration

These details can significantly affect the installation.

Measuring Sliding Doors

For a sliding door, record:

  • Overall width
  • Overall height
  • Number of panels
  • Sliding direction
  • Fixed-panel locations
  • Screen requirement
  • Floor level

Photographs of the threshold area are particularly helpful for replacement work.

Measuring Stacker Doors

Stacker doors can have several moving panels.

Record:

  • Overall opening width
  • Overall height
  • Desired stacking direction
  • Number of panels if known
  • Screen requirements

The available opening width influences the panel layout.

Measuring Bifold Doors

Bifold door measurement should include:

  • Width
  • Height
  • Opening direction
  • Folding direction
  • Threshold detail

Bifold systems can be sensitive to level and squareness, making final measurement especially important.

Measuring Hinged Doors

For hinged doors, also record:

  • Left- or right-hand hinging
  • Inward or outward opening
  • Sill or threshold detail
  • Adjacent sidelights

A marked sketch can prevent handing errors.

Measure Door Threshold Conditions

The threshold should be photographed and measured carefully.

Identify:

  • Internal floor level
  • External paving level
  • Step-down
  • Drainage
  • Existing sill
  • Waterproofing interfaces

Door threshold coordination is particularly important for weather performance.

External Paving and Door Measurement

External paving should not automatically be assumed to finish at the same level as the internal floor.

The relationship between:

  • Door sill
  • Paving
  • Drainage

should be properly coordinated.

Measuring Before Flooring Is Installed

If finished flooring has not yet been installed, establish the expected finished floor level.

This may include:

  • Tiles
  • Timber flooring
  • Carpet
  • Screed

Door heights and thresholds should be coordinated with the final floor level.

Measuring After Flooring Is Installed

If flooring is complete, measure from the appropriate finished surface.

Still confirm whether the new frame needs to sit:

  • On top of the finished floor
  • At a lower structural level

The installation detail determines this.

Measuring Window Sill Heights

Sill height is the distance from the finished floor level to the bottom of the window.

This can be important for:

  • Furniture
  • Benchtops
  • Privacy
  • Fall-prevention considerations
  • Architectural alignment

Measuring Window Head Heights

The window head should be checked against:

  • Ceiling
  • Door heads
  • Other windows
  • External façade lines

Consistent head heights can improve architectural appearance.

Measuring Windows Above Kitchen Benches

Check:

  • Finished floor level
  • Benchtop height
  • Splashback
  • Window sill

Do not rely on a generic kitchen bench height if the joinery design has already been specified.

Measuring Bathroom Windows

Bathroom windows may need to coordinate with:

  • Tiles
  • Vanities
  • Showers
  • Privacy glass
  • Ventilation

The final sill position should be reviewed before ordering.

Measuring Windows Near Stairs

Windows near stairs can involve additional considerations because the effective floor level can vary along the opening.

Relevant project requirements should be established before final manufacture.

Measuring Floor-to-Ceiling Windows

Record:

  • Structural floor level
  • Finished floor level
  • Structural head
  • Finished ceiling or lining level

Large glazing should also be checked for transport and installation access.

Measuring Large Windows

Large windows should be measured particularly carefully because even a small dimensional error can create significant installation problems.

Also consider:

  • Access
  • Crane requirements
  • Vacuum lifting
  • Transport route

Measuring Multiple Windows

Give every window a unique reference.

For example:

  • W01
  • W02
  • W03

Then record:

  • Width
  • Height
  • Type
  • Room
  • Glass
  • Colour

This reduces confusion on larger projects.

Use a Window Schedule

A simple window schedule can include:

Window Width Height Type Glass Colour
W01 1200 1500 Awning Double glazed Black
W02 1800 1500 Sliding Clear Black
W03 2400 2100 Fixed Double glazed Black

For quoting purposes, even a basic schedule can make pricing much more efficient.

Measure Each Opening Separately

Do not assume two openings that look identical are exactly the same size.

Measure each opening.

This is particularly important in older buildings.

Photograph Every Opening

Photos can reveal details that measurements alone do not show.

Useful photographs include:

  • Whole window internally
  • Whole window externally
  • Head
  • Sill
  • Left jamb
  • Right jamb
  • Surrounding wall

Put a Tape Measure in the Photo

For preliminary quoting, a photograph showing a tape measure against the opening can help provide context.

However, the photo should not replace final verified dimensions.

Label Your Photos

Match photos to the window references.

For example:

  • W01 inside
  • W01 outside
  • W02 inside
  • W02 outside

This becomes particularly important when pricing an entire house.

Can I Measure Windows From Architectural Plans?

Yes, for quotation purposes.

Architectural plans and schedules can often provide:

  • Dimensions
  • Configuration
  • Opening direction
  • Glass requirements

However, final site dimensions may still need verification before manufacture depending on the project.

Can EZ Windows Quote From Plans?

Yes.

Builders, architects, developers and homeowners can provide plans and window schedules for quotation.

This is often the most efficient approach for:

  • New homes
  • Renovations
  • Townhouses
  • Commercial projects

Can I Measure From a PDF?

PDF plans can provide useful dimensions for pricing.

However, do not scale dimensions from an electronic drawing unless the scale and document accuracy are reliable.

Written dimensions should generally take precedence over visual scaling.

Preliminary Measurements vs Manufacturing Measurements

This distinction is important.

Preliminary measurements

Used for:

  • Budgeting
  • Quoting
  • Comparing options

Manufacturing measurements

Used to physically manufacture the product.

Manufacturing dimensions require a much higher level of certainty.

Can Homeowners Measure Their Own Windows?

Yes, for preliminary quotation purposes.

A homeowner can provide:

  • Approximate width
  • Approximate height
  • Photos
  • Window type

This is often enough to start a price discussion.

Final dimensions should then be confirmed according to the agreed project responsibility before manufacture.

Who Is Responsible for Final Measurements?

Responsibility depends on the accepted project scope.

It may be:

  • Customer
  • Builder
  • Installer
  • Architect
  • EZ Windows where measurement is expressly included

The responsible party should approve the final manufacturing dimensions.

Why Shop Drawings Matter

Shop drawings can help confirm:

  • Overall dimensions
  • Window configuration
  • Mullions
  • Transoms
  • Opening direction
  • Glass
  • Colour

Complex or architectural projects should be reviewed carefully before approval.

Approved Shop Drawings

Once shop drawings are approved for manufacture, they become an important production reference.

They should therefore be checked carefully.

Review:

  • Sizes
  • Quantities
  • Configuration
  • Glass
  • Colour
  • Handing

before approval.

Do Not Approve Drawings Without Checking Dimensions

A drawing can look visually correct while containing an incorrect dimension.

Every relevant dimension should be reviewed before approval.

Measuring Windows With Shrouds

Where aluminium window shrouds are used, the shroud dimensions must be coordinated with the actual window.

EZ Windows generally allows approximately 10 mm clearance between the window size and the internal shroud dimension, subject to the particular design and approved drawings.

Fixing lugs can add approximately 3 mm, which should also be allowed for where relevant.

These details should be coordinated before fabrication rather than assumed after manufacture.

Measuring Awning Windows With Shrouds

Awning windows need sufficient room for the sash to open without contacting the shroud.

Consider:

  • Shroud depth
  • Internal opening dimension
  • Window position
  • Sash projection

before finalising the detail.

Measuring Windows Before Shrouds Are Ordered

Ideally, the window and shroud should be coordinated from the same approved dimensions.

This reduces the risk of:

  • Insufficient clearance
  • Poor alignment
  • Opening interference

Measuring for Flyscreens

Flyscreens are generally designed to suit the selected window system rather than simply the wall opening.

Specify whether screens are required when the window is ordered.

Measuring for Security Screens

Security-screen requirements should also be identified early.

They can affect:

  • Frame selection
  • Clearances
  • Window configuration

Measuring Replacement Windows With Existing Blinds

Existing blinds can affect access and internal clearances.

Where necessary, record:

  • Blind position
  • Reveal depth
  • Handle clearance

This can help avoid clashes.

Measuring Around Curtains

Curtains generally do not determine the window manufacturing size, but their placement can influence:

  • Handle access
  • Internal appearance

This is more of a design coordination issue than a frame-sizing issue.

Measuring for Window Shutters

Where external or internal shutters are proposed, coordinate their dimensions and fixing zones with the window system.

Common Window Measuring Mistakes

Common errors include:

  • Measuring only once
  • Mixing width and height
  • Measuring the glass instead of the frame or opening
  • Assuming the opening is square
  • Forgetting installation clearance
  • Ignoring reveal depth
  • Ignoring finished floor levels
  • Forgetting opening direction
  • Measuring multiple windows as if they are identical
  • Ordering before installation details are resolved

Measuring the Glass Instead of the Window

If you are ordering a complete new window, the glass dimension is not the correct measurement.

Measure the relevant:

  • Opening
  • Frame
  • Wall condition

depending on the project.

Measuring Only the Existing Sash

The moving sash is also not the same as the complete window size.

For replacement, the whole installation must be understood.

Forgetting Floor Levels

This can create serious problems with doors.

Always identify whether the measurement is taken from:

  • Structural slab
  • Screed
  • Finished tiles
  • Finished timber flooring

Forgetting External Levels

External paving or decking can affect:

  • Threshold clearance
  • Drainage
  • Door operation

Photograph external conditions when requesting a replacement-door quote.

Ordering Before the Opening Is Ready

On new construction, early ordering can create risk if the actual openings have not yet been built or checked.

Where site measurements are required, ensure the openings are sufficiently complete to measure reliably.

Measuring for Supply-Only Windows

For supply-only orders, responsibility for dimensions is especially important.

EZ Windows manufactures according to the approved order information.

The customer or responsible project party should therefore ensure the supplied manufacturing dimensions are correct.

How Accurate Should Window Measurements Be?

Manufacturing dimensions should be accurate enough for the specified product and installation method.

Do not round dimensions casually.

Record the actual measurement in millimetres.

Can Openings Vary by a Few Millimetres?

Yes.

Small variations are common in building work.

The window size and installation allowance should account for reasonable construction variation.

Can a Window Be Made Smaller Than the Opening?

Yes.

The frame is generally manufactured to allow appropriate installation clearance.

However, excessive gaps are undesirable.

The correct size should be determined from the actual installation conditions.

What Happens if the Window Is Too Big?

An oversized custom window may:

  • Not fit the opening
  • Require building modification
  • Require product alteration
  • Need remanufacture

This can create significant cost and delay.

What Happens if the Window Is Too Small?

An undersized window can create:

  • Excessive perimeter gaps
  • Poor appearance
  • Difficult fixing
  • Additional finishing work

Correct measuring is therefore essential.

Can a Custom Window Be Easily Resized After Manufacture?

Not necessarily.

Aluminium windows are fabricated around approved dimensions.

Significant dimensional changes after manufacture may require substantial modification or complete remanufacture.

Does Glass Affect Final Measurement?

The overall window measurement determines the frame.

The selected glass is then manufactured to suit that window system.

However, very large or specialised glazing can influence what frame configuration is practical.

Does Window Type Affect Measurement?

Yes.

The basic opening width and height may be the same, but different products can require different considerations.

For example:

  • Awning windows need external opening clearance.
  • Sliding windows need the desired sliding direction.
  • Doors need threshold coordination.
  • Bifolds require accurate level and squareness.

How to Send Measurements to EZ Windows

A useful quote request can include:

  • Project address or suburb
  • Window reference
  • Width
  • Height
  • Window type
  • Quantity
  • Glass
  • Colour
  • Screens
  • Photos
  • Plans if available

Keep measurements clearly labelled.

Example Window Measurement

W01 – Living Room

Width: 2400 mm
Height: 1800 mm
Type: Fixed + Awning
Glass: Double glazed
Colour: Black
Quantity: 1
Installation: Required

This is far more useful than simply sending:

“Large living room window.”

Example Sliding Door Measurement

D01 – Family Room

Width: 3600 mm
Height: 2400 mm
Type: Sliding door
Configuration: 3 panels
Glass: Double glazed
Colour: Charcoal
Screen: Required
Installation: Required

Photos and plans can then be added.

Measuring and Aluminium Window Prices

Accurate dimensions allow more meaningful pricing.

Approximate measurements may be sufficient for initial budgeting, but the price can change if final sizes differ significantly.

This is why preliminary and final measurements should be clearly distinguished.

Measuring and Lead Times

Manufacturing normally cannot proceed until the required dimensions and specification have been approved.

Delays in:

  • Measuring
  • Shop drawings
  • Colour selection
  • Glass selection

can affect the overall project programme.

Measuring and Compliance

Measurement determines whether the product fits.

It does not by itself establish all project compliance requirements.

Other considerations may include:

  • Wind pressure
  • Safety glazing
  • Energy performance
  • Fall prevention
  • Structural openings

These should be established by the responsible project parties.

EZ Windows Scope and Measurements

EZ Windows manufactures products according to the approved dimensions and agreed scope.

Unless specifically included, EZ Windows should not be assumed to be responsible for:

  • Structural opening design
  • Surrounding building structure
  • Flashing design
  • Waterproofing design
  • Engineering certification

Where final measurement is provided by another project party, those dimensions should be verified and approved before manufacture.

Frequently Asked Questions About Measuring Aluminium Windows and Doors

How do I measure an aluminium window?

Measure the width and height in several locations and check the diagonals to determine whether the opening is square.

Do I measure width or height first?

Record dimensions as width × height.

Should I measure in millimetres?

Yes. Millimetres provide the most useful format for window and door quotations and manufacture.

Should I measure the glass?

Not when ordering a complete new window. The glass is only one component of the window.

Do I measure the existing frame?

For replacement work, the existing frame may be one useful measurement, but the actual installation method determines the final manufacturing size.

How many times should I measure the opening?

Measure width and height at several points rather than relying on one measurement.

Why should I measure the diagonals?

Diagonal measurements help identify whether the opening is square.

What if my window opening is out of square?

Record the variation. The final window sizing and installation method should account for the actual opening.

Should the new window be the exact same size as the hole?

Not generally. Installation clearance is usually required.

How much clearance should I allow?

There is no universal allowance for every installation. It depends on the frame, wall and installation method.

Can I measure windows myself for a quote?

Yes. Preliminary homeowner measurements and photos can often be used for pricing.

Can I measure my own windows for manufacture?

Responsibility depends on the agreed scope. Manufacturing dimensions need to be accurate and approved.

Can EZ Windows quote from plans?

Yes. Architectural plans and window schedules can be used for quotations.

Do you need photos?

Photos are highly useful for replacement projects because they show surrounding conditions.

How do I measure a sliding door?

Measure the overall opening width and height and provide the desired panel configuration, sliding direction and threshold details.

How do I measure a bifold door?

Measure width and height carefully and check the opening for level, plumb and squareness.

How do I measure an awning window?

Measure the opening and also check external clearance for the opening sash.

How do I measure a replacement window in brick?

Measure the visible frame, brick opening and internal opening where accessible, then establish how the old window will be removed.

What is reveal depth?

Reveal depth relates to the depth through the wall or window reveal and can affect internal finishing and installation position.

Should I measure every window separately?

Yes. Do not assume similar-looking openings are identical.

Can old houses have different window sizes?

Yes. Older buildings frequently have substantial variation between openings.

Should I wait until flooring is finished before measuring a door?

Not always, but the final finished floor level must be established and allowed for.

Can wrong measurements be fixed after the window is made?

Sometimes minor adjustments may be possible, but significant dimensional errors can require remanufacture.

Get Your Aluminium Window and Door Measurements Ready for a Quote

Understanding how to measure aluminium windows and doors makes the quoting and ordering process much easier.

For an initial EZ Windows quotation, send:

  • Width
  • Height
  • Window or door type
  • Quantity
  • Glass preference
  • Colour
  • Screen requirements
  • Project location
  • Photos
  • Plans where available

Preliminary measurements can be used to start the pricing process.

Before manufacture, final dimensions and specifications should be checked and approved by the responsible party under the agreed project scope.

Accurate information at the beginning reduces uncertainty later and helps ensure custom aluminium windows and doors are manufactured for the actual requirements of the project.

EZ Windows — Architectural precision, designed to perform.

Do It Easy.