Calculation method
Usable fabric width is the bolt width less unusable edges. Divide total track width times fullness by usable width; round up to whole fabric drops and allow at least one drop per finished panel. Add top and hem allowances to the finished drop, then round the cut length up to a full vertical repeat. Convert all drops to linear yards and round to the supplier increment.
Worked example: inputs to material quantity
A 72 in track, two panels, 2× fullness, 54 in fabric with 2 in unusable edges, 84 in finished drop, 4 in top and 8 in hem, and 12 in repeat needs 3 drops. The 96 in cut is already repeat-aligned; 3 × 96 ÷ 36 = 8 yd.
What the estimate covers
All dimensions are user-entered. Round quantities and order sizes against your supplier’s current stock; the page does not design structural, drainage, or suspension systems. The related guide explains each assumption and common measurement mistakes.
Product and method reference
The external source offers installation or measurement context; the arithmetic and illustrative defaults here are stated separately. British Institute of Interior Design window measurement and fabric calculation paper.
Calculation and editorial review: November 3, 2026. Arithmetic runs in your browser; project inputs are not submitted to TwoCut.