Before you order and install your new windows, you need to determine the correct window size. This is made simple with our handy step-by-step window measuring guide. For further information about measuring window accessories and add-ons, please refer to our window measurement guide.

What do you need?

Pen
Paper
Measuring tape
Blueprint, if necessary

Please note: with the person measuring remaining inside, both the inside and outside of the window should be measured with the dimensions noted in millimetres. Any additional window fittings, such as frame extensions or top mounted roller shutters, should also be included when measuring.

1. Sketch your window

Please sketch your window on a piece of paper, indicating the handle's location and opening direction with the tip of a triangle, as displayed in our image. This drawing will be useful again later when it comes to noting down your window’s dimensions.

2. Measure the window's width

Please measure the full width of your wall’s opening, once at the top and once at the bottom. If these measurements differ, please note down the smaller value. A slight installation allowance for the new frame should then be deducted. Please see the guide on installation allowances below.

Example: white window with a width of 1000 mm

► 1000 mm - (2 x 10 mm installation allowance) = 980 mm

3. Measure the window's height

Please measure the full height of your wall’s opening, once on the left-hand side and once on the right. If these measurements differ, please note down the smaller value. A slight installation allowance for the new frame should then be deducted. Please see the guide on installation allowances below.

Example: white window with a height of 900 mm

► 900 mm - (2 x 10 mm installation allowance) = 880 mm

Installation allowance guide

Installation allowances are a necessary part of measuring windows and ensure that new frames sit firmly in their openings. The amount of allowance depends on the width and colour of the window’s profile.

Please note: The specifications are per side.

Approximate window size	Installation allowance for a white window	Installation allowance for a coloured window
1000 mm	10 mm	15 mm
2000 mm	15 mm	20 mm
3000 mm	20 mm	25 mm

More step by step guides for measurement

Measure patio door

Measure front door

Measure roller shutters

Measure window sill

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