Short answer
Rough guide: a single headshot fits a 5 x 7 ft backdrop or a 53 in roll. One person full length needs about 6 to 7 ft of width plus a floor sweep. Two to four people full length need a 107 in roll or wider. Use the calculator for your exact lens, sensor and room.
Backdrop you need
How the calculator works
- Frame at the subject. Framing sets how tall the frame must be (about 1.6 ft for a headshot up to 6.8 ft for full length). People set how wide. The frame takes your sensor’s shape, so whichever need is larger decides it.
- Camera distance. Distance = focal length x frame height / sensor height. An 85 mm lens on full frame framing a 4.8 ft three quarter portrait vertically sits about 11 ft away.
- Project back to the backdrop. The frame grows by (camera distance + gap) / camera distance. We add 10 percent slack, then compare with real paper widths (53, 86, 107 and 140 in) and common fabric sizes.
- Floor sweep. If the bottom of the frame reaches the floor at the backdrop, you need a sweep at least as long as the gap plus about 1.5 ft under the feet.
When your room is too small
- Shoot tighter. Three quarter instead of full length removes the sweep and saves height.
- Turn the camera. A vertical frame of one person needs less width than a horizontal one.
- Close the gap a little. Below about 3 ft, shadows and spill show, so light the backdrop separately. See how to light a backdrop.
- Extend in post. Many photographers stretch the backdrop edges in editing for horizontal crops. It works best on plain paper.
Questions people ask
Why does the backdrop need to be wider than my subject?
Your lens sees a cone that keeps widening behind the subject. At the backdrop, several feet behind them, the same frame covers more width than it does at the subject. The farther back the backdrop, the wider it has to be.
Does a longer lens need a smaller backdrop?
Yes, for the same framing. A longer lens is used from farther back, so the extra distance to the backdrop is a smaller share of the total, and the cone widens less. That is why portrait photographers in small studios often use 85 mm or longer.
What does sweep mean?
The part of the backdrop that curves from the wall onto the floor and runs under and in front of the subject. You need one whenever the floor shows in the frame, which is almost always for full length shots.
What should I enter for a phone?
Choose full frame and type the phone lens equivalent focal length, often listed as 24 or 26 mm for the main camera and longer for telephoto. Phones report their lenses in full frame equivalent millimeters.
Is the result exact?
No. It is geometry with simple assumptions: an adult standing, a level camera at the frame center, and about 2 ft per person (1.6 ft for tight framings). Poses, props and cropping change it, so leave some extra.
Sources
Last reviewed October 29, 2026. Sizes, colors and listings change; check the product details before you buy, and follow the maker’s care instructions.