Don't make any deductions, we'll deduct from the width to ensure your blind fits perfectly. For example, if your inside recess is 100cm wide, we will make the blind material to 96.5cm wide and then once the end fittings are applied the overall width will then be 100cm wide. Measure the full width and height of the recess and then add a little extra to the top and to each side, we will make the blind to the size you specify with no deductions.
To minimize light sneaking through we recommend that the blind overlaps the window recess by at least 7cm so add this to your measurement. For example, if your measurement is 100cm wide, we will make the blind material to 100cm wide and then once the end fittings are applied the overall width will then be 103.5cm wide.