How to measure a double glazed window

Note: This is only for a basic general guideline, Norman & Underwood Glazing would send out one of our fitters to fully measure and estimate prior to fitting.

There are a number of reasons that you may be looking for a replacement double glazed window. The glass may be damaged or you may wish to change the look of an existing window, such as changing a standard pane for stained or leaded glass. You may currently have single glazing and wish to update an existing window to a more efficient double glazed window.

To place an order for a double glazed window you will need to provide measurements to the window company. It is important to be accurate with these measurements to make sure the replacement window fits properly.

When measuring for replacement double glazed glass or for a whole replacement window you will need to measure:

  • Width
  • Height
  • Depth

Measuring a double glazed window

If you are looking to replace the whole unit, frame and glass, you will need to provide the measurements of the opening. You should take the measurements from the outside of your house and start with the width first. To measure for a new double glazed window you should:

  • Take three measurements of the width from the top, middle and bottom.
  • Measure from the jambs of each window, not from the existing windows or frames.
  • The smallest measurement across the three measurements is the size you need to give the window company.

Measuring the height of double glazed windows

The next measurement you will need is the height of the window. This should be measured from the surface closest to the window on the sill to the top of the window opening.

You should measure the height of the window on the left, right and at the centre. The smallest of these three measurements is the height of your new double glazed window.

Measuring double glazed window thickness

You will need to provide the depth of the window opening to make sure the new double glazed unit will fit correctly. This measurement should be the thickness of the opening from the exterior to the interior. Ignore any existing window strips, profiles or fixings as these will be removed when the replacement double glazing is fitted.

Measuring double glazed windows for replacement glass

The window frames may not need replacing, you may simply need a new double glazed glass unit to fit inside an existing frame. If the frames are intact and there is no damage to the locks or trims you will only need replacement double glazed glass.

When measuring for replacement glass only you will need to:

  • Measure the width from the beading on each side of the uPVC frame
  • Measure the height from the beading on the top and bottom of the frame
  • Deduct 10mm from each measurement

It is important to be accurate as the glass cannot be changed once it is custom made to your measurements. If you have a damaged window, want double glazing fitted or need emergency glass repair or replacement, the experienced window installers at Norman & Underwood Glazing can help. Our installers can visit the property, take measurements and provide a free quotation, so simply call us on 0116 231 8000 today.