How to Measure a Double Glazed Unit for Replacement
You don't need to measure a unit yourself to get a repair booked — we're always happy to measure up on-site — but if you'd like a rough quote in advance, or you're just curious what's involved, here's how it's done properly.
Measure the visible glass, not the frame
The measurement that matters is the visible glass size, once the bead has been removed — not the outer frame dimensions. As a rough guide before we visit, measure the visible glass width and height (the bit you can see and touch) to the nearest 5mm.
- Width: measure straight across the visible glass at the mid-point, side to side
- Height (drop): measure straight down the visible glass at the mid-point, top to bottom
- Measure twice and note the smaller figure if the two don't quite match — frames are rarely perfectly square
Check the unit thickness
Double glazed units come in a range of overall thicknesses (commonly around 20–28mm for standard double units, more for triple glazing) made up of two glass panes and a spacer bar. This is very difficult to measure accurately without removing the bead, which is one of the main reasons we prefer to measure on-site or work from a bead-off photo.
Note the glass type and features
A few extra details help us quote accurately without a wasted visit.
- Is the glass clear, obscure (patterned/frosted), or does it have Georgian bars?
- Is there any tint, or a coloured spacer bar around the edge?
- Does the window face a busy road, or is noise/security a concern? (helps us suggest laminated glass if useful)
- Take a photo of the whole window as well as a close-up of the misted or cracked area
Why we still like to measure ourselves
Even with good measurements from you, older frames are rarely perfectly square, and the exact spacer bar depth needs checking against the bead depth to make sure the new unit sits flush. That's why our fixed price is always confirmed after we've measured or reviewed clear photos — it protects you from any surprise adjustments on the day.
Want a professional to handle it?
Get a quoteCall Mark on 07535 916982 or request a callback.
Related repairs we handle
Covering Central London and out to the M25
Frequently asked questions
Do I need to remove the bead myself to measure?
No — please don't attempt to remove the bead yourself, as it can damage the frame or the remaining glass. A rough width and height of the visible glass is all we need for an initial estimate.
What if my measurements are slightly out?
That's completely normal and expected — your figures just help with a ballpark quote. We always take exact measurements ourselves before ordering the replacement unit.
Can I send a photo instead of measuring?
Yes — a clear photo of the whole window plus a close-up of the affected pane, along with a rough size, is often enough for us to give a fixed price over the phone.
Does the same process apply to a cracked pane as a misted one?
Yes — the same visible glass measurements and photos help us quote whether the glass is misted, cracked, or being upgraded to a different spec.
Call Mark on 07535 916982 or request a callback.