No matter if you’re replacing a single window or all of the windows on a property, accuracy is essential for ensuring you achieve the best result. Therefore, you need to know how to be able to properly measure up replacement windows. So, we’ve created this handy guide to help installers and DIYers alike to be able to accurately measure up all types of window replacement.

Measuring the width of replacement windows

anthracite-grey-upvc-casement-window-lawtonWhen measuring the width of a window, make sure you do so from the outside opening (brickwork opening) and never measure the old frame. Next, do the following:

1. Measure the width of the window at the top, middle and bottom of the window opening.

2. Determine which is the narrowest measurement and deduct 10mm from it. This will be the width of the window that you need to order.

3. Repeat this process to find the width for every window that you need to measure up.

Measuring the height of replacement windows

Residence 9 windowsLike you did when measuring the window width, you should take measurements from the outside opening and never measure the old window frame. Next:

1. Take measurements of the window’s height from the left side, middle and right side.

2. Deduct 10mm from the shortest measurement of the 3 just taken and this will be the height of the window that you need to order.

3. Repeat this process to find the height for every window that you need to measure.

Measuring the depth of replacement windows

uPVC slimline windows in GreyYou need to measure window depth correctly otherwise you run the risk of the new windows being too deep to fit into the opening that will be left by the windows being replaced. To measure the depth of a window, you need to:

1. Measure the distance from the outside of the frame to the inside and take the measurement from edge to edge of the window frame.

2. Repeat this step in several places around the window frame and the smallest measurement that you’ve taken should be the depth of the window that you need to order.

3. Repeat this process to find the depth of every window that you need to measure.

What about measuring up bay and bow windows?

The processes for measuring bay and bow windows is slightly different because of the complexity of their designs. However, provided you follow our guidance, you should be able to find some accurate measurements for them.

Square bay windows

upvc square bay windowSquare bay windows have three sides along with 90-degree corner posts and the process for measuring them is as follows:

1. To measure the internal width, which will be the back span, you need to measure the distance from one edge of the existing frame to the other.

2. Next, measure the width of each side window from one edge of the frame to the other. Be sure that you take these measurements internally too and that the two side windows are the same size.

3. Measure the height from brick to brick but make sure to include any existing cill. Unlike the other two measurements, the height should be measured externally.

4. To find the external width, you will need to combine the internal width with the depth of the two 90-degree corner posts. So, for corner posts which have a frame depth of 70mm, you will need to add 140mm to the measurement you took for the internal width.

Bow windows

slimline uPVC bow windowAs bow windows have two or more sides and are less angular than their bay counterparts, you might find measuring them is more difficult. The process for measuring them is as follows:

1. Measure the internal width (back span) from one edge of the existing frame to the other.

2. Taking each measurement internally, measure the width of each individual window from one edge of the frame to the other.

3. Next, you need to find the projection of the bow. To do this, measure the distance internally from the inside back span of the window to the inside point of the window frame. Repeat this step for each window to find the projection at every point.

4. For the height, take the measurement externally, measuring from brick to brick and making sure to include any existing cill.

3 tips when measuring up replacement windows

1. Measure in millimetres – millimetres are more precise than inches so make sure you measure in them to ensure your chosen fabricator is able to produce windows that will fit more accurately.

2. Double-check your measurements – this might sound obvious but precision is of the utmost importance and if you get the measurements incorrect, it will be your responsibility, not the fabricators.

3. Order any uPVC windows from us! – we’re one of the leading uPVC window suppliers We offer competitive prices, use a range of leading uPVC systems and have over 35 years’ experience which we’re happy to share with you to help you get more for a window project you’re working on.

For more information on My Trade Windows or to request our services, give us a call on 01483 361152 or contact us online.