How to measure a window for a roller blind
A blind is measured differently to a pole or a track: there's no stack-back to allow for, but the fit is far less forgiving. Here's the method we'd use before ordering one.
A curtain pole or track is measured generously and dressed to suit; a blind is measured to the window itself, and the wrong number either jams in the recess or leaves a gap either side that lets the light straight through. Get the fitting method and the width right, and everything else follows.
First, choose recess fit or exact fit
This decision comes before any measurement, because it changes what you measure.
Recess fit
The blind sits inside the window reveal, brackets fixed to the top or sides of the opening. Neat and built-in, but needs at least 4 to 5cm of usable depth so the brackets clear a window handle or lock.
Exact fit (outside the recess)
The blind fixes to the wall or ceiling above the opening instead. The safer choice on a shallow or obstructed recess, and it blocks more light at the edges since the blind overlaps the frame.
Measure the width
For a recess fit, measure the width of the opening in three places: top, middle and bottom, with a steel tape, and use the narrowest figure. Brickwork and plaster settle unevenly, so the recess is rarely a perfect rectangle; the narrowest measurement is the one the blind actually has to clear.
For an exact fit, measure the width of the opening itself and add roughly 5cm to each side (10cm total) so the blind overlaps the frame and blocks the light at the edges, checking first that there's a clear, flat surface to fix to across that width.
Buy the size up, then trim
Our blackout roller blinds come in fixed widths (60, 90, 120, 150, 180 and 210cm, depending on colour) with a 175cm drop, and trim down on site to your exact measurement: the fabric and the roller both cut to size with everyday tools. Always buy the next width up from your measurement, never the size below. A blind that's too wide can be trimmed to fit; one that's too narrow cannot be made wider.
This is a fixed-width, trim-to-fit range, not a bespoke made-to-measure service. If your window falls well outside 60 to 210cm wide, or needs a drop other than 175cm, get in touch before ordering and we'll tell you honestly whether it'll work.
Check the drop and any obstructions
The 175cm drop suits most standard windows with room to spare below the sill; the blind simply hangs at whatever length is drawn down. Before fixing anything, check for a window handle, lock or sill lip that would catch the blind or stop it lying flat, particularly on a recess fit, and confirm there's enough depth for the bracket to sit clear of the glass.
Common questions
Recess fit or exact fit, which should I choose?
Recess fit sits inside the window reveal for a neat, built-in look, but needs at least 4 to 5cm of usable depth so the brackets clear the handle. Exact fit is fixed to the wall or ceiling above the opening, is the safer choice on a shallow or obstructed recess, and blocks more light at the edges because the fabric overlaps the frame.
Why measure the width in three places?
Window openings are rarely perfectly square: brickwork and plaster settle unevenly over time. Measuring the top, middle and bottom of the recess and using the narrowest figure guarantees the blind will actually fit, rather than jamming against the wider point.
Which width do I actually buy?
Our blackout roller blinds come in fixed widths and trim down on site, so buy the next size up from your measurement and cut the fabric and roller to fit exactly. Buying short is not recoverable; buying the size up and trimming always is.
Do you make blinds to a bespoke size?
Not yet: our current roller blind range comes in fixed widths from 60cm to 210cm with a 175cm drop, trimmed down to your exact size on site. A true made-to-measure service (any width, any drop) is not available at the moment.