Measure the hanging position
Use the rail or usable section of the pole as your reference. Window width alone does not necessarily describe the area the curtain must cover. Decide the position and opening arrangement before measuring the required width.
In the example, the rail is 2 m wide. With a fullness factor of 2, the planned flat fabric width becomes 2 × 2 = 4 m across the complete curtain arrangement.
Choose panels and finished drop
With two equal panels, each must provide 4 ÷ 2 = 2 m of flat width. The calculator splits the total equally. It does not model unequal panels or sewing systems that need a different distribution.
Measure the drop from the reference point required by your hanging system to the intended lower edge. The example uses a finished drop of 2.4 m. Do not include the hem or top allowance in this finished measurement.
Separate finished size from cutting length
Finished drop and cutting length are different. A 2.4 m drop, a 0.2 m hem allowance and a 0.1 m top allowance require 2.7 m per fabric width before any adjustment for pattern repeat.
Check what your sewing plan includes in each allowance, such as folds and heading details. The example fullness is not a universal recommendation. Before cutting, compare every measurement with the actual fabric and construction method you intend to use.
- Measure from the actual suspension reference.
- Record finished drop and sewing allowances separately.
- Check that your panel arrangement is symmetrical.
Frequently asked questions
Should I measure the window or the pole?
Measure the usable width that the installed curtain needs to cover. Take that reference directly instead of inferring it from the window.
Does fullness add vertical length?
No. It multiplies the required flat width. The hem, top allowance and pattern repeat affect the cutting length of each fabric width.