Practical guide

Measuring your windows yourself

You do not need to measure windows for a quote with millimetre precision online — a surveyor does the exact figures later. But taking a few rough sizes yourself makes your online estimate sharper and helps you plan. Here is a simple, safe way to do it.

What you will need

A basic tape measure, a pen and paper, and a couple of minutes per window is all it takes. Work at ground level wherever possible and never lean out of or reach across an upstairs window — an approximate size taken safely from inside is worth far more than a precise one taken from a risky position. Remember these numbers are only for the online estimate, so being a centimetre or two out will not cause any problems.

How to take the measurement

Measure the visible width of the window from one side of the frame to the other, then the height from top to bottom. Do this in millimetres if you can, and jot both figures down next to a note of which window it is — for example “lounge front” or “back bedroom”. If a window is not a simple rectangle, note its rough shape too. There is no need to remove trims or dig into the brickwork; the surveyor handles all of that when they confirm the exact sizes.

A quick tip for accuracy

Windows are rarely perfectly square, especially in older homes, so if you want to be a little more thorough you can measure the width in two or three places and the height on both sides, then use the smallest reading. Again, this is only to make your online figure realistic — the fitted units will be made from the surveyor’s official measurements, which they take responsibility for. Never order windows from your own numbers.

Count and describe as you go

While you have the tape out, count how many windows you want replaced and note their style — casement, sash, bay or fixed — and any details like an obscured bathroom pane or a difficult-to-reach opening. This descriptive information often shapes the estimate as much as the sizes do, and it gives installers a clear picture of the job before anyone visits.

Once your rough measurements are ready, you can put them to good use. It is worth seeing how sizes and specs affect pricing by exploring a tailored double glazing quote and keeping an eye on current deals and honest pricing as you plan.

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