The method

How this calculator works

Measure from the hanging point

The drop starts where the curtain hangs, which is not always the top of the pole or track. For curtains on rings, measure from the ring eye. For tracks, measure from the glider or hook. For eyelet curtains, measure from the top of the pole, allowing for the small amount of fabric above the eyelets.

If the pole or track is not yet fitted, plan its position first and measure from there. The hanging point sits slightly below the pole itself, so measure again once the hardware is up.

Choose the finish

A floor-length curtain commonly finishes about 1 cm above the floor, so it hangs cleanly without catching on the carpet. A sill-length curtain finishes just above the sill. A below-sill curtain finishes lower, commonly 10–15 cm below the sill, so it covers the edge of the sill and any apron below it.

Puddled curtains, which rest on the floor, need extra length that is a style choice. This calculator does not include that, so add the extra you want to the finished drop.

Check across the window

Floors, sills and poles are not always level. Measure the left, centre and right of the window and use the shortest figure to avoid dragging. Check for radiators, window seats or furniture that the curtain must clear.

For made-to-measure curtains, the maker will ask for the drop in a particular way and will add the heading and hem themselves. Follow their instructions rather than adding extra yourself.

Worked example

Example: a hanging point at 215 cm

  1. For a floor-length finish, the curtain ends 1 cm above the floor, so the drop is 215 − 1 = 214 cm.
  2. For a below-sill finish with the sill at 100 cm, the curtain ends 15 cm below it, at 85 cm above the floor, so the drop is 215 − 85 = 130 cm.
  3. For a window frame topping out at 200 cm, fixing the pole or track 10–15 cm above gives 210–215 cm.

Practical answer: Floor-length curtains need a finished drop of about 214 cm, and below-sill curtains about 130 cm. Check these against the nearest ready-made size or give them to your curtain maker.

Before you buy

Common measuring mistakes

  • Measuring from the top of the pole instead of the ring eye or glider.
  • Measuring to the floor on one side only when the floor is not level.
  • Choosing a drop that leaves the curtain dragging, or so short that it stops halfway down.
  • Fixing the pole before checking for pipes and cables, or before deciding where the curtain will finish.
  • Adding hem and heading allowances to a made-to-measure order that already includes them.