Home / Guides / How to measure a window for blinds or shades
How to measure · Blinds
How to measure a window for blinds or shades
Measuring for blinds goes wrong in one place: people take one width and one height. Windows aren't square. Here's the method the pros use — measure three, and know which way to round.
First: inside or outside mount?
This decides everything else. Inside mount sits the blind inside the window recess (clean, built-in look; needs enough depth). Outside mount mounts on the wall/trim above the opening (covers an out-of-square or shallow window, blocks more light). Decide first — the measuring and the rounding are opposite. Full comparison →
Measure width at three heights, height at three widths
- Width — measure the opening at the top, middle, and bottom. For inside mount, use the narrowest of the three (so it clears). For outside mount, use the widest plus your desired overlap.
- Height — measure left, centre, right. Inside mount: use the longest. Outside mount: from where the headrail sits down to the sill (or lower).
- Depth (inside mount only) — how deep is the recess? It must clear the headrail; too shallow forces an outside mount.
The rounding rule — this is where money is lost
Inside mount: round the width down to the nearest 1/8 in — the factory then takes its own small deduction so the blind clears the frame. Never add for inside mount, and never take the deduction yourself. Outside mount: add your overlap (typically 3–4 in total width, 2–3 in above) so it covers the gap and blocks side light.
Blinds aren't on the shelf yet
We're launching curtains, screens and weatherstrip first, then blinds (they carry a US cordless-safety standard and hardware shipping we're validating). The measuring is identical — get on the blinds early-access list →
FAQ
Do I add or subtract when measuring for inside-mount blinds?
Neither — give the exact narrowest width. The factory takes a small standard deduction so the blind clears the frame. If you deduct too, it'll be too narrow. Only outside mount gets an overlap you add yourself.
Why measure the width three times?
Windows settle out of square. The top, middle and bottom widths often differ by 1/4 inch or more; for inside mount you must use the narrowest so the blind fits the tightest point.
Early access
Be first when window ordering opens.
We already cut outdoor cushions and covers to size at MeasuredPatio. Windows are next — curtains, screens, weatherstrip, then blinds. Leave your email and we'll bring you in first, with a founding-order discount.
You're on the list. We'll email you the moment window ordering opens — nothing else. ✓
One email at launch. No newsletter. We keep your measurements out of it until you ask.