It is important that measurements are taken at the point where the track is to be installed. If the track is to be fitted external to the window aperture then please allow for any overhang required. If the curtains are to open clear of the window the tracks should be aperture size plus a min of 30% (although this is better left to your own judgement)
If you are fitting directly to a window frame or within a recess then measure the recess size but ensure you deduct enough room to allow the curtains to wrap around the drive units.
We recommend the use of a metal tape measure as the use of cloth tapes may not be accurate.
If you need any assistance please call us and we would be pleased to help