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1. Use metric not imperial

The first rule of thumb is to make sure you take accurate measurements in millimetres not inches. This gives you a finer level of accuracy and means there’s no room for error if we have to convert the measurement to metric.

2. Measure the opening outside

So firstly step outside. You need to take height and width measurements for the brickwork opening. Bear in mind that the height measurements must be from underneath any existing removable windowsill. If your property is rendered, simply take off a little of the render and measure to the brickwork edge.

3. Measure brick to brick in at least three different places

Remember the opening may not be exactly square so take a minimum of three measurements – top, middle and bottom, for the height and the same again for the width. This means your window manufacturer can get an accurate view of the exact size of the space the finished product will be fitted into. The final width and height measurement the manufacturer will use is the smallest one.

Measuring the Height
Measuring the Width

4. Deduct 10mm (yes, really!)

This sounds like odd advice but you need to take off 10mm from the final height and width measurements. This is to allow for a small fitting allowance around the new frame and means the fitter can make sure the new window frame sits squarely when it’s in place. Any gaps are then fitted with spacers and filled to keep the frame in just the right position.

5. Never measure the old frame

This is a common error and certainly one to avoid. Ignore the old window frame – this is going because it is no longer suitable. Consider the fact that it may well have warped so the last thing you want to do is take measurements from it!

6. Be sure of your measurements

Make sure you check (and double-check) your measurements so you are 100% sure you have them correctly. This is important because we will not accept responsibility for incorrect measurements and you will still have to pay for a window that doesn’t fit. If you are unsure, consult a professional installer or builder and give yourself total peace of mind.

7. Cill measurement

Taking all the above information in to account, when inputting your measurements we require you to provide us your overall brick-to-brick measurement minus the 10mm fitting tolerance. We will automatically include the cill in to the measurements you provide us – pending you require one that is!

If you struggle, or you would like us to contact you for piece of mind, once your order is placed just leave a note at the checkout asking for a call back!

How to Measure Bay Windows

Square Bay windows consist of three sides and two 90 degree corner posts. The width (back span) will need to be measured internally from the existing frame edge to edge. Measure each side window internally and ensure they are the same from one edge of the frame to the other. The height will need to be measured externally brick to brick including any existing cill.

We will add 140mm to the external size for the two 90 degree corner posts which are 70mm square.

For example, if the internal width is 1800mm the external width including two 70mm corner posts will be 1940mm, see image below.

How to Measure Bay Windows

Bow windows are slightly more complicated than bays, consisting of two or more sides and shallower angles. The width (back span) will need to be measured internally from the existing frame edge to edge. Measure each individual window internally from one edge of the frame to the other. The projection of the bow will need to be measured internally from the inside back span of the window to the inside point of the window frame as below image. The height will need to be measured externally brick to brick including any existing cill.