How to size curtains
Measure the surface, then the overhang
Curtain width: total panel width should be 2–2.5× the rod length for a full, gathered look. Curtain length: floor-length (just touches the floor), trouser-length (1″ of pooling), or apron-length (just below the windowsill). Always measure rod-to-floor, not windowsill-to-floor.
Standard sizes vs. your actual surface
Manufactured "standard" sizes assume textbook measurements. Older homes, custom furniture, and non-standard windows often deviate by 1–3″. If the measurement falls between two stock sizes, choose the larger; it's easier to hem or tuck excess fabric than to add length you don't have.
Mounting and clearance
Hang the rod 4–6″ above the window casing and extend 6–12″ past each side — this makes the window look larger and lets curtains stack off the glass when open. Standard panel widths are 50″ and 100″; standard lengths are 63″, 84″, 95″, 108″, and 120″.
Common mistakes
- Measuring once. Surfaces are rarely perfectly square; take the smallest of three measurements.
- Forgetting shrinkage. Cotton items can lose 3–5% on the first wash.
- Ignoring drape. Heavier fabrics need an extra inch or two to hang correctly.