I found this really useful guide for measuring curtains and blinds (from Direct Blinds) and thought it would be a useful thing to share with you all. It’s the one thing that I get asked all of the time so thank you to Direct Blinds for this great description.
You will need a metal tape measure cloth tapes are not accurate enough and a pen and paper to write down the sizes. You can measure your window in centimetres CM, millimetres MM, or Inches. If you want your blind to fit or hang outside your window opening or recess we call this Exact size.
When measuring for roller blinds remember that the cloth or fabric width will be 3cm narrower than the overall width.
Measure the total width of the rail or pole excluding any finials and add 250mm (10″) overlap which allows the hanging curtains to overlap in the centre when closed. This is the track/pole width.
Measure from the top of the track or the small eye on the ring of the pole to 12mm(½”) from the floor or 150mm (6″) below the sill.
If fitting curtain rails or poles they should be fitted 150mm (6″) above the window recess and extend approximately 200mm (8″) either side. This is the HEM TO HEM drop.
Measure the distance from the top of the pole to 12mm (½”) above the floor (or approximately 35mm (1½”), if you have not yet had carpet fitted but intend to) or 150mm (6″) below the window sill. This is the POLE (TOP) TO HEM drop.