How to use the curtain size calculator
Ordering curtains from the glass size alone usually leaves panels that look skimpy or rods that block the view when open. This tool builds rod width, finished panel width, drop and fabric quantity from the window, mount style and fullness.
- Choose units and mount. Outside mount adds an overhang past the frame; inside mount uses the recess width.
- Enter window width and height, plus how far the rod sits above the sill and how far the sill is above the floor.
- Pick drop style and fullness, and whether you want a pair or a single panel.
- Set fabric width, heading and hem, and a pattern repeat if the cloth has one. Add a waste percentage for cutting mistakes.
Curtain sizing formulas
Rod width = window width + 2 × overhang (outside) | = window width (inside)
Total curtain width = rod width × fullness
Width per panel = total ÷ number of panels
Finished drop = f(rod height, window height, floor clearance, style)
Cut length per width = finished drop + heading + hem (rounded up to pattern repeats)
Widths needed = ceil(total curtain width ÷ fabric width)
Fabric = widths × cut length × (1 + waste); yards = inches / 36, metres = cm / 100
| Fullness | Look | Best for |
|---|---|---|
| 1.5× | Tailored, light gather | Heavy drapery, modern flats |
| 2× | Standard gather | Most living rooms and bedrooms |
| 2.5× | Full, luxurious | Sheers, pinch pleats, formal rooms |
Worked examples
A 60 × 60 in window, floor-length pair
Outside mount with 8 in each side gives a 76 in rod. At 2× fullness the total curtain width is 152 in, or 76 in per panel. With the rod 4 in above the sill and 36 in from sill to floor, a floor float drop is 4 + 60 + 36 − 0.5 = 99.5 in. On 54 in fabric you need ceil(152/54) = 3 widths. Cut length 99.5 + 8 + 8 = 115.5 in; with 10% waste, fabric ≈ 3 × 115.5 × 1.1 / 36 ≈ 10.6 yd.
Inside-mount sill curtains
A 120 cm wide recess with inside mount uses a 120 cm rod. At 1.5× fullness a pair needs 90 cm finished width each. Drop to the sill equals the window height if the rod sits at the top of the recess. Fewer widths of fabric are needed than a full-length outside mount.
Patterned fabric with a 64 cm repeat
If the cut length before matching is 280 cm, round up to the next multiple of 64 cm (5 × 64 = 320 cm). That extra length is what keeps motifs aligned across joined widths and is why patterned cloth often needs more metres than plains.
Who this calculator helps
- Interior designers specifying soft furnishings and checking fabric budgets.
- Homeowners and DIYers ordering rods and made-to-measure or sew-your-own panels.
- Workrooms and makers turning window schedules into cutting lists.
- Staging and rental teams standardising curtain packages by unit type.
Practical tips
- Plan wall coverings and paint with the wallpaper calculator and the paint calculator.
- Check window light and WWR with the window-to-wall ratio calculator and the daylight factor calculator.
- Mount rods high and wide to make windows feel larger; many designers place the rod halfway between the trim and the ceiling.
- Stack-back needs space: lined blackout pairs can eat 6–12 in each side when open.
- Buy matching lining and interlining from the same cutting batch when colour continuity matters.
Want to try curtain colours and fabrics in the real room first? Restyle a photo with Room Redesign.
