Measure the opening in millimetres, take the width and the height in three places each, and note which measurement came from where. Then decide whether the shutters sit inside the window reveal or on the face of the wall, because that one decision changes every number you take.
What you want in your hand first
A steel tape, not a fabric one. A pencil, and a sheet of paper with a rough sketch of each window so the numbers have somewhere sensible to live.
Work in millimetres the whole way through. Shutters are made in millimetres, and switching between centimetres and millimetres halfway through a house is how a panel ends up 100mm short.
Inside the reveal, or on the face
A reveal fit sits the frame inside the window opening, tight to the plaster or render. It looks built in and keeps the sill clear, and it needs the reveal to be deep enough to take the frame plus the louvres behind it.
A face fit mounts the frame on the wall or the architrave around the opening. It covers the reveal edges, hides an opening that is out of square, and it is what you use when there is not enough depth to go inside.
Shallow reveals are common in older brick homes and in newer places with thin plasterboard returns. If the reveal cannot take the frame and still leave the louvres room to rotate, you are looking at a face fit or a slimmer frame.
Taking the width and the height
For a reveal fit, measure the width at the top, the middle and the bottom of the opening. Measure the height on the left, the centre and the right. Openings are rarely square, and the smallest of those numbers is the one that governs the job.
Do not take a deduction off yourself. Write down exactly what you measured and let whoever makes the shutter apply the tolerances, because the allowance changes with the frame being used.
For a face fit, decide how far past the opening you want the frame to sit on each side and at the top, then measure that overall size instead. More overlap means fewer light gaps and a better look on a crooked opening.
The depth question installers always ask
Reveal depth decides whether a reveal fit is possible at all. The frame uses some of it, then the louvres need clearance to rotate inside the panel without catching on the plaster or the glass.
Louvres come in 63mm, 89mm and 114mm. The wider the louvre, the more room it needs to swing, which is why a 114mm louvre in a shallow reveal is a conversation rather than an order.
Check what is already sitting in the opening. Window winders, handles, flyscreen frames and security screens all eat depth, and a winder that fouls a closed louvre is the single most common thing missed on a home measure.
Panel layout and which way things swing
Width decides how many panels you get. A panel that is too wide becomes heavy and eventually sags on its hinges, so a wide window is split into several narrower panels instead.
Hinged panels swing into the room. Before you settle on a layout, open an imaginary panel and see what it hits, especially near a kitchen bench, a bed head, a door or a heater.
Bi-fold panels hinge to each other and fold back on themselves, which suits wide openings and sliding doors where a single swing would block the walkway. Running them on a track keeps the stack tidy at one end.
Motorised roller shutters measure differently
If roller shutters are also on your list, the numbers are not the same as plantation shutters. You need clearance either side of the opening for the guide rails, and height above the opening for the headbox that houses the rolled up curtain.
Those shutters are motorised, so there is also a cable to get from the headbox back to a switch or a power point. Downpipes, corners, meter boxes and window hoods all affect what fits, and they are far easier to sort out on site than over the phone. Our shutter range and the electric roller shutter options have the detail on both.
Shutters are made to the millimetre for your opening, so a wrong number cannot be let out or taken up later. If you want the numbers checked, or you would rather not climb over a kitchen bench with a tape, book a free measure and quote and we will do it properly.
Common questions
Should I measure the window or the opening for shutters?
Measure the opening, then say which fit you want. For a reveal fit, take the inside of the opening at three points each way and use the smallest. For a face fit, measure the overall size you want the frame to cover, including the overlap onto the wall.
How deep does a window reveal need to be for plantation shutters?
Deep enough to take the frame and still leave the louvres room to rotate, which means a 114mm louvre needs more depth than a 63mm one. Winders, handles and flyscreens use depth too, so they have to be measured, not assumed.
Do I take a deduction off my measurements?
No. Write down the raw measurements and let the maker apply the tolerance, because the allowance depends on the frame and the fit. Taking your own deduction on top of theirs is how shutters end up loose in the opening.