How to Measure a Window for a Roman Blind

01/06/2017, 10:30

Roman blinds can be a stunning addition to your home, but only if you choose the right size of blinds, and doing that means measuring your windows properly. It’s a good idea to take each measurement twice, and use a reliable, metal tape measure with measurements in millimetres, so you can get the perfect size.


Ember Thermal Roller Blind- Black

Before you measure your windows, draw up a sketch of them, and then write the measurements on the sketch as you go.

Inside or Outside Mount?

Outside mounts are preferable to inside mounts, because they allow the blind to be pulled completely back from the window, and will not block out any light when they are open. Choose an inside mount if there is not enough space around the window to allow the blinds to be fitted properly.

Measuring for an Outside Mount

  1. Measure the width of the window, from the left to the right outside edge. Take three measurements – one from the top of the window, one from the middle, and one from the bottom.  If the window has a frame or architrave, measure to the outside edges. If it does not have a frame or architrave, measure the full width of the opening.  Take the biggest of the three measurements, and add 100mm to that width. This will allow an overlap of 50mm worth of blind to sit on each side of the window, ensuring that the blinds block out light well and provide good thermal insulation. If you have shelving or anything else near the window you may need to adjust the excess to take those obstacles into account.
  2. Measure from the top of the architrave or frame, to the bottom (or the full length of the window opening, if necessary). Take three measurements – one on the left, one on the right, and one in the middle. Add 200mm to the longest measurement, to allow the blinds to hang above the window, and another 50-100mm to allow the blind to extend below the window. If there are obstacles above or below the window, reduce these measurements to take them into account.

Measuring for an Inside Mount

  1. Measure the exact width of the window, in millimetres, from the top, middle and bottom of the window. Use the smallest of the three measurements, with a small amount of space allowed on each side, to allow the blinds to move freely when they are opened and closed.
  2. Measure the exact height of the window, from the top of the frame to the top of the sill. Again, take three measurements – from the left, right and middle of the window, and take the smallest of the three measurements.

Windows are almost never perfect rectangles or squares, which is why it’s so important to take three measurements. This is why it’s also a good idea for the blind to hang below the sill, so it does not accentuate any areas where the window is not square.

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