Window treatments · rod placement
Curtain rod height and width calculator.
Enter the floor-to-frame height, window width, ceiling height and fullness. You get the rod height (4 to 6 in above the frame by default, never closer than 2 in to the ceiling), the rod length, the total and per-panel curtain width, and the length to the floor. Inches or centimetres. Runs in your browser; nothing is sent or stored.
Window and ceiling
Rod and curtains
Worked example
The top of the frame is 72 in off the floor, the ceiling is 96 in, the window is 48 in wide, fullness 2, a pair of panels, the rod 5 in above the frame and 5 in beyond each side, and a 1 in gap above the floor. Rod height = 72 + 5 = 77 in (19 in below the ceiling, so no cap applies). Rod length = 48 + 2 x 5 = 58 in. Total panel width = 48 x 2 = 96 in, so 48 in per panel. Curtain length = 77 - 1 = 76 in, so the next ready-made length is 84 in.
Method
Plain arithmetic. Rod height = floor to frame top + the distance above the frame, lowered if needed so at least 2 in remains below the ceiling. Rod length = window width + the extension on both sides. Total panel width = window width x fullness, shared across the panels. Curtain length = rod height - the gap you want above the floor, compared with the ready-made lengths 84, 96 and 108 in.
Guides disagree. Taskrabbit says one-half to two-thirds of the way from the trim to the ceiling (or 4 to 6 in above the trim when space is tight) and 4 to 6 in beyond each side; Drapery Rods Direct says halfway between the casing and the ceiling for standard drapes and 4 to 10 in beyond the casing; The Shade Store suggests about 12 in beyond the frame. The defaults above are editable. Fullness follows the definition in the Deconovo guide (total panel width divided by window width), so it is measured against the window, not the rod. Rings, brackets and finials are not modelled.
Rule of thumb, not a standard. These are design rules of thumb from published decorating guides, not building codes or standards. Treat the result as a starting point and tape it out in the room before you buy or drill. Results are shown in both imperial and metric. Conversions use 1 in = 2.54 cm and 1 ft = 0.3048 m.
Sources, each opened 2026-10-08:
- How High to Hang Curtains (Taskrabbit Blog): rod at one-half to two-thirds of the way from the window trim to the ceiling, or about 4-6 in above the trim when space is tight, never closer than 2 in to the ceiling, 4-6 in beyond each side, standard lengths 84, 96 and 108 in.
- Tips for Hanging Curtains (Drapery Rods Direct): a different rule: halfway between the casing and the ceiling, and 4-10 in beyond the casing.
- How to Install Curtain Rods: Placement and Hanging Guide (The Shade Store): suggests about 12 in beyond the frame on each side.
- Curtain Fullness Guide: How Wide Should Curtains Be for a Luxurious Look? (Deconovo): fullness ratio = total panel width / window width; 1.5x, 2x and 2.5x.
- NIST Guide to the SI, Appendix B.8: Factors for Units Listed Alphabetically (NIST): lists 1 inch = 2.54 cm, 1 foot = 0.3048 m and 1 footcandle = 10.76391 lux.
Frequently asked questions
How high should I hang the curtain rod above the window?
Taskrabbit gives a rule of thumb of one-half to two-thirds of the distance from the window trim to the ceiling, or about 4 to 6 in above the trim when space is tight, with at least 2 in left between the rod and the ceiling. The calculator defaults to the tight-space 5 in figure. Drapery Rods Direct instead suggests halfway between the casing and the ceiling for standard drapes, and The Shade Store suggests 8 to 10 in above the frame on cathedral ceilings. The field is editable.
How far should the rod extend past the window?
Taskrabbit says the rod should extend 4 to 6 in beyond either side of the frame, which makes the curtains 8 to 12 in wider than the window. Drapery Rods Direct gives 4 to 10 in and The Shade Store about 12 in, so use the number that suits your room.
How wide should curtains be?
Deconovo defines fullness as total panel width divided by window width and lists 1.5x as basic, 2x as luxurious and 2.5x as designer. The calculator multiplies your window width by the fullness you choose. For fabric quantities use the curtain fabric calculator.
How long should the curtains be?
The calculator works from the rod height down to the gap you want above the floor, then shows the next ready-made length. Taskrabbit notes that ready-made curtains typically come in 84, 96 or 108 in. The floor gap is a style choice, not a rule.
What happens if the rod would hit the ceiling?
The calculator lowers the rod so it stays 2 in below the ceiling, following the minimum in the Taskrabbit guide, and tells you it did so.