The short version of how to measure for venetian blinds: decide whether the blind sits inside the reveal or on the wall, then measure the width and the drop in three places each. For an inside fit, check the reveal depth as well, because venetian slats need room to tilt. Give us the raw numbers and let the factory take off the deductions.
Pick the fit before you pick up the tape
A venetian either sits inside the window reveal or fixes to the wall or architrave in front of it. Inside looks built in and leaves the architrave on show. Outside covers more glass, cuts light at the edges and hides a crooked opening.
The two use different numbers, so make the call first and write it at the top of your sheet. If you cannot decide, our guide to inside and outside mount blinds sets out the pros and cons of each.
Measuring inside the reveal
Measure the width across the top, the middle and the bottom of the reveal. Use the narrowest figure, because the blind has to clear the tightest point to go up and down without rubbing.
Then measure the drop on the left, in the centre and on the right, from the underside of the head down to the sill. Write all three down. If they differ by more than a few millimetres the sill is out of level, and that is worth knowing early, because the bottom rail of a venetian is dead straight and will show it.
Use a steel tape and work in millimetres. Round down, never up, and do not take anything off for clearance yourself.
Check the reveal depth
Leaving this one out is the usual mistake. Every time you tilt a venetian, each slat swings through its full width, so the reveal needs clear depth of at least the slat width plus a little to spare.
Measure from the front edge of the reveal back to the first thing that sticks out. That might be the glass, but it is often a winder handle, a lock, a flyscreen track or the window frame itself. A 50mm slat in a reveal with 45mm of clear depth will knock the handle every time it tilts.
If the depth is tight, there are two ways out. Go to a 25mm slat, which needs about half the room, or fix the blind outside the reveal. Our guide to slimline and 50mm venetian blinds compares the two in more detail.
Measuring for a face fit
Here you are covering the window rather than fitting into it. Measure the opening, then add overlap at each side so light cannot spill round the edges. In a bedroom, around 150mm past the glass at each side is a good working figure if the wall allows it.
For the drop, decide where the headrail will sit and measure from there to where you want the bottom rail to finish, usually a little below the sill. Note anything on the wall that will get in the way, such as a light switch, a curtain track or a cupboard close to the window.
Allow for the stack
When a venetian is pulled all the way up, the slats pile into a stack under the headrail. Inside a reveal, that stack sits across the top of the glass, and you lose that strip of view whenever the blind is up.
Thin aluminium slats stack tight. Wooden venetian blinds have thicker slats and stack deeper, so on a tall window the band across the top is noticeable. If you want the whole window clear during the day, fix the blind higher on the wall so the stack sits against the plaster instead of the glass.
Controls and the details people forget
A venetian runs on a tilt wand and a lift cord. Decide which side each one goes on before you order, because it is set when the blind is made.
- Put the controls on the side you reach first, and away from a bed head, a basin or a door swing.
- Note handles, locks and anything sitting on the sill that the bottom rail would land on.
- Check what the wall above the window is made of. Plaster, brick and timber all take a different fixing.
- On a wide window, think about two blinds instead of one. A very wide venetian gets heavy to lift, especially in timber.
- Under the Australian rules a loose cord must not be able to form a loop of 220mm or more within 1600mm of the floor, so plan where the cleat will go on a low window.
Measure every window separately, even ones that look identical. In older brick houses, two windows on the same wall can be several millimetres apart.
Measuring yourself is a good way to get a rough idea, but we measure every window before anything is made, and Steve does that measure himself. Each headrail is cut in our own Sydney factory to the opening we measured, not the nearest stock size. Have a look at the venetian blinds range, then Book a free measure and quote and we will check the depth, the stack and the control side at every window.
Common questions
Should I take deductions off my measurements?
No. Give us the raw reveal sizes and tell us whether you want an inside or outside fit. We apply the clearance in the factory, and if you take it off as well the blind ends up with double the gap down each side.
What if my window is not square?
That is common in older Sydney homes, and a reveal can easily be narrower at the bottom than at the top. Use the narrowest width for an inside fit. If the difference is large, an outside fit hides it far better than a blind sitting in the reveal.
How deep does a reveal need to be for a venetian?
At least the width of the slat plus a little clearance, measured to the nearest handle or lock rather than to the glass. A 25mm slimline slat fits most shallow reveals. A 50mm slat needs a bit more than 50mm clear, or the blind goes on the wall instead.
Do I measure the glass or the reveal?
For an inside fit, measure the reveal, from one side of the recess to the other. For an outside fit, measure the area you want covered, including the architrave and the overlap at each side.
Can I order the same size for windows that look the same?
It is safer not to. Windows that look identical are often a few millimetres apart, especially in older brick houses, and a few millimetres is enough for a blind to rub or leave a gap. Measure each one and label it by room.