Advanced options
Recess fit: retailers deduct ~1cm from the width for clearance; measure width at top, middle and bottom and use the SMALLEST. Outside fit: add ~5cm each side and ~10cm above so light doesn't leak round the edges. Check the retailer's own instructions: some deduct for you (order recess size exactly), some don't.
What The Blind Size Calculator Works Out
- Order size, inside the recess: the recess width minus 1 cm of clearance for the mechanism, by the full drop. Recesses are never square, so measure the width at the top, middle and bottom and use the smallest; one centimetre is the difference between a blind that glides and one that grinds.
- Order size, outside the recess: the recess width plus 5 cm each side and 10 cm above, because light finds every gap the overlap does not cover. Blackout blinds, especially with side channels, work far better outside-mounted for the nursery's 5am.
- Measuring tips: metal tape not fabric, millimetres written not remembered, and a check for the window handle sweep, tile lips, trickle vents and telephone points before ordering.
- Clearance deduction and retailer convention (advanced): retailers split into two camps: some deduct the clearance themselves and want the exact recess size, others ship the millimetres you order. The deduct-or-not convention is the industry's one refusal to standardise, so pick the option that matches your retailer's measuring guide.
- Outside-fit overlaps (advanced): edit the side, top and bottom overlaps. A sill that stops the blind needs 0 below; a blind hanging past the sill wants 5 to 10 cm below for full coverage.
- Blind type and recess depth check (advanced): each type needs a minimum recess depth to sit flush: about 6 cm for a roller, 7.5 cm for venetians, 9 cm for verticals and 10 cm for Romans with their fabric bulk. Perfect-fit and intu frames clip into uPVC beading and skip both drilling and the depth question; the table shows which types fit your recess.
- Order size in millimetres (advanced): most made-to-measure order forms work in millimetres, width before drop, since transposition is the returns desk's other best customer.
- Blind area and cost (advanced): the finished blind's fabric area and an estimate at your price per m2 for all identical windows, with a GBP 25 minimum per blind. Made-to-measure rollers run about GBP 30 to GBP 60 per m2, Romans and wooden venetians GBP 80 to GBP 150. Looped cords strangle: child-safety rules require breakaway connectors and cleats, and cordless or motorised operation removes the hazard outright.