Measuring your own windows for blinds, done properly

Recess fit or face fit: decide this first

Recess fit means the blind sits inside the window reveal, so the frame, sill and any handles are still visible. Face fit means the blind is mounted on the wall or frame above and hangs over the whole opening, which is the only option if the recess is too shallow, out of square, or blocked by a handle.

Measure the depth of the reveal before you decide. As a rough guide you need at least 60 to 70mm of clear depth for most brackets, more for a chunky Venetian headrail, and if a window handle protrudes into that space recess fit is off the table regardless of width.

• Recess fit: measure the width in three places (top, middle, bottom) and use the smallest.
• Recess fit: measure the drop in three places (left, middle, right) and use the smallest.
• Face fit: measure the full width and height you want covered, then add coverage on top.

Roller blinds

For a recess roller, take the smallest width measurement and do not round up. A roller that is even 3mm too wide will bind against the reveal every time it is raised or lowered. For a face fit roller, add roughly 100 to 150mm total width and 70 to 100mm of drop coverage above the window so light does not sneak in around the edges.

Venetian blinds (aluminium and wood)

Venetians need slightly more tolerance than a roller because the headrail is boxier. Measure the recess width at its narrowest point and deduct a further few millimetres for bracket clearance. Wood Venetians in particular need a genuinely square opening, since a slat that is not sitting level shows immediately.

Vertical blinds

Verticals are usually specified as a headrail width and a drop to floor, ceiling or sill depending on the room. Measure the drop with the tape held taut, not slack, because a vertical louvre that is even 15mm too long will drag and twist at the bottom.

Roman blinds

Roman blinds are almost always face fit because the folded fabric needs to sit above the recess when raised. Measure the full width you want to cover and the full drop from the fixing point to the sill or floor, and remember the stacked fabric will sit roughly 150 to 200mm deep at the top when fully raised, so check nothing above the window is in the way.

Perfect fit blinds

Perfect fit systems clip into the bead of a uPVC or aluminium window without drilling, so the measurement that matters is the sightline of the window itself, not the recess. This is genuinely fiddly to get right on an existing frame, and it is the one product on this list we would always recommend having measured professionally.

Where people go wrong most often

The three repeat mistakes we see are: measuring a bay window as one continuous width instead of three separate blinds, measuring a recess without checking whether the window opens outward into it, and rounding a measurement to the nearest whole centimetre out of habit. Every one of those turns into a blind that does not fit properly.

If any of this is starting to feel like more variables than you bargained for, that is completely normal, and it is exactly why the home consultation exists.

Why we still measure for free

Our home consultation includes expert measuring at no cost, whether you order that day or not. We would rather spend twenty minutes checking a reveal for square than have you order a blind that arrives 4mm out on a window that looked perfectly straight from across the room.