Search for "standard window sizes" and you will find tables that contradict each other, because Spain has no official standard window size. The name is given to whatever sizes each manufacturer or DIY superstore keeps in stock, and those sizes match your opening only some of the time. In a 1970s block of flats or an old village house, almost never.
Below you will find the most common sizes by room as a reference, the size limits of a uPVC window depending on its hardware and, most importantly, how to measure the opening step by step and which figure to enter in the configurator so your made-to-measure window fits first time.
The most common "standard" sizes by room
These are the sizes most searched for on Google in Spain and the ones that come up most often in off-the-shelf catalogues, given as width × height, in centimetres, frame included.
| Room | Common sizes (width × height, cm) | Sashes |
|---|---|---|
| Bathroom and WC | 40 × 40, 50 × 50, 60 × 60, 60 × 80 | One, often tilt-and-turn |
| Kitchen | 80 × 100, 100 × 100, 120 × 100 | One or two |
| Bedroom | 100 × 120, 120 × 120 | Two |
| Living room | 140 × 120, 150 × 120, 180 × 120 | Two, sometimes with a fixed pane |
| French door | 80 × 200, 120 × 200, 150 × 200 | One or two |
Of all these sizes, the one searched for most on Google is 120 × 120. Even so, "common" does not mean it will work for you. If your opening measures 117 × 123, a 120 × 120 window will not go in, and a 110 × 120 one leaves a gap you have to fill with packers and foam, which means extra work for the fitter and a wider joint for heat to escape through.
Why made to measure, and how big a window can be
A made-to-measure window is built to the millimetre for your opening. The fitter only has to level and seal it, and you end up with thin, even joints all round the frame.
The limits are set mainly by the hardware, the part that holds the sash and lets it swing. With Winkhaus activPilot hardware, a side-hung or tilt-and-turn sash can be 400 to 1200 mm wide and up to 2450 mm high with full warranty cover; with Axor K3, up to 1000 × 2390 mm. Beyond those widths the window is split into two or more sashes. The whole unit can reach 3200 mm per side and 6 m² in area.
Even within those limits, a window more than a metre wide usually gets two sashes. A 1.2 m sash holds up fine, but when it is open it takes up half the room and feels heavy in the hand. French doors follow the same logic with taller sashes.
How to measure the opening step by step
You need a steel tape measure, a pencil and ten minutes per window. Write everything down in millimetres, the unit the window is made in.
Start with the width, at three heights: top, middle and bottom. Measure brick to brick, between the walls of the opening, not between the frames of the old window if it is coming out. Then the height, also at three points (left, centre and right), from the sill (inside or outside) to the lintel. From each set of three, keep the smallest figure, because no opening is perfectly straight and the window has to fit through its narrowest point.
Then measure both diagonals, corner to corner. If they differ by more than a centimetre, the opening is out of square; the window can still be made, but your fitter should know beforehand. Finally, note which way each sash opens (always looking at the window from inside the house), whether there is a roller shutter with a box above it and what type, and take a photo of the opening from inside and outside. With all that, the order leaves no room for doubt.
Many openings have a sub-frame (premarco), a frame of aluminium or wood fixed to the wall before the window goes in, which acts as its base. In new builds it is standard; in a renovation it depends on what the fitter finds when the old window comes out. If the sub-frame stays, measure inside it. If it is coming out, measure without it, even if that means waiting until the old window has been removed.
Which size to enter in the configurator
This is the step where the most expensive mistakes happen. The factory makes the frame exactly to the size you enter, to the millimetre, without deducting anything. If you enter the size of the opening as it is, the window will be the size of the opening and will not go in, because the fitter needs a gap all round to level it, pack it and fill the joint with foam. The "Window frame size" field takes the outside size of the frame, that is, the opening minus the fitting gap.
The German RAL fitting guidelines, the industry reference, recommend a gap of at least 10 mm per side for white uPVC windows up to 1.5 m, 15 mm up to 2.5 m and 20 mm up to 3.5 m. For coloured or woodgrain uPVC, which heats up more in the sun and expands more, add 5 mm to each figure. For a 1200 × 1200 mm opening and a white window, for example, you take 10 mm off each side and order 1180 × 1180. If your fitter works with a different gap, use theirs, since they are the one who will be fitting it.
If you want a roller shutter, the configurator lets you order it together with the window and asks how you measured, with the box included in the height or only the opening the slats cover. We explain this in more detail on the roller shutters page.
Before you confirm the order
The window is made exactly to the sizes you give in the order, to the millimetre. That is why measuring correctly is the responsibility of whoever places the order, and a made-to-measure window cannot be returned on the grounds that it does not fit. The safest option is for the same fitter who will install it to do the measuring: they know the opening, know what gap they need and can see the state of the sub-frame.
With your measurements in hand, enter the width and height in the configurator, choose the profile, glass and opening type and see the price straight away. Check the summary before you confirm and, if any figure does not add up, get in touch before the window goes into production.