Venetian blinds are one of the most forgiving window coverings you can buy, but only if they are made to the right size. A blind that is a few millimetres too wide will not fit inside the recess; one that is too narrow lets light leak at the sides. This guide shows you how to measure for made-to-measure aluminium venetian blinds in about ten minutes, with nothing more than a steel tape measure, a pencil and a notepad.
Before you start: what you need
- A steel tape measure. Fabric or paper tapes stretch and give wrong readings.
- A pencil and paper to write down every measurement, in centimetres.
- A few minutes per window. Measure every window separately, even if they look identical: openings in the same room often differ by several millimetres.
Step 1: decide inside or outside the recess
This is the most important decision, because it changes what you measure.
Inside the recess
The blind sits within the window opening, fixed to the top of the recess. It gives a clean, built-in look and leaves the wall around the window free. Choose this option when the recess is deep enough for the headrail and the tilted slats, and when nothing sticks out of the window frame.
Outside the recess
The blind is fixed to the wall or to the frame above the window and overlaps the opening on all sides. Choose this option when the recess is shallow, when a window handle or tilt-and-turn sash would hit the slats, or when you want less light around the edges.
Step 2: measure for an inside-recess blind
- Width: measure the width of the opening at the top, in the middle and at the bottom. Write down the smallest of the three values.
- Height: measure the height on the left, in the centre and on the right, from the top of the recess to the window sill. Write down the smallest value.
- Depth: check how deep the recess is at the top, and look for anything that could block the slats when they tilt: handles, hinges, window locks, tiles or curtain rails.
Enter the opening size exactly as you measured it. Do not make any deductions yourself: in the Window-All configurator you choose "inside the recess" and we apply the fitting tolerance for you, so the blind slides in and still covers the glass.
Step 3: measure for an outside-recess blind
- Measure the width and height of the opening as above.
- Add an overlap on each side so the blind covers the opening fully. Around 5 cm on the left and right and 5 to 10 cm above the opening is a common choice; add more if you want a darker room.
- Check that there is a flat surface for the brackets at the height you have chosen, and that the blind will not hit a radiator, a sill or a door frame when lowered.
For an outside-recess blind, enter the finished size of the blind you want, overlap included. We make it to that size.
Common measuring mistakes to avoid
- Measuring only once. Walls and recesses are rarely perfectly square. Three readings for width and three for height prevent surprises.
- Mixing up width and height. Always write width first, then height (for example 100 × 150 cm).
- Rounding up. Write the exact value. Rounding up by even half a centimetre can stop an inside-recess blind from fitting.
- Forgetting the handle. On many European windows the handle sits inside the recess. If tilted slats would touch it, mount the blind outside the recess.
- Deducting the tolerance twice. If you subtract a few millimetres yourself and the configurator applies the tolerance as well, the blind ends up too narrow.
Which window suits an aluminium venetian blind?
Aluminium blinds with 25 mm slats are light, hard-wearing and moisture-resistant, which makes them a natural fit for kitchens, bathrooms, home offices and small windows where a slim profile matters. You tilt the slats to direct the light and lift the blind to clear the window completely. If you want a warmer look for a living room or bedroom, compare them with our wooden venetian blinds. If you prefer fabric to slats, read our guide on choosing the right made-to-measure roller blind.
Ready to order? Get your exact price
Our made-to-measure aluminium venetian blind starts from €44. Open the configurator, choose inside or outside the recess, enter your measurements and colour, and you will see the exact price before you pay.
- Shipping: Italy €7.90, EU countries €12.90, USA €24.90 (duties paid by the recipient).
- We confirm the production and dispatch date by email within 2 business days.
- Questions about your window? Write to us through the contact form.
Measure once, carefully, and your blind will fit the first time. And if insects are a problem in summer, pair your blind with a pleated mosquito net, measured the same way.