How to Measure a UPVC Window

Window Measuring Guide

How to Measure a UPVC Window

These guidelines are to help you measure for a new replacement upvc window and make an accurate measurement.

Measure the opening outside on both the height and width. Always measure the exact brickwork opening and not the old window frame.

Measure brick to brick in at least three different places and deduct 10mm from both the final height and width measurements to allow for 5mm fitting allowance around the new window frame. This will enable you to ensure the new frame sits plumb and square once in the aperture. Spacers and filler will then be required to secure the frame into place and fill any gaps.

Measuring the Window Width

Measuring the Window Height

Please remember:

Do not measure your existing window or frame but measure the brick opening.
Measure in at least three different places and deduct 10mm from both the final height and width measurements - we do not make any fitting allowances on the sizes you provide.
Measurements will need to include the window frame, cill and any frame extenders/add on’s required.
All dimensions to be supplied in metric and all styles viewed externally.

Transom Drop

The transom drop is measured from the top of the outer frame and down to the centre of the horizontal bar.

Mullion Width

The mullion is measured from the outer edge of frame to the centre of the vertical bar.

How to measure a double glazed square bay window

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.

measuring a bay window

How to measure a double glazed bow window

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.

measuring a bow window

Please note: We are unable to accept responsibility for incorrect measurements. If you are unsure we recommend that you consult a professional window fitter, joiner or builder to measure. You can always call us on 01530 515161 and we will gladly help and advise.