Motion-picture film is measured by length, but directors and editors think in running time. The bridge between them is the number of frames in each foot of film, which depends on the gauge and the pull-down: 16 mm film carries 40 frames per foot, standard 35 mm 4-perf carries 16, and 3-perf – popular because it saves a quarter of the stock – carries 21⅓. Multiply the length by frames per foot to count frames, then divide by the frame rate to get the running time.
At the cinema standard of 24 frames per second, 35 mm 4-perf runs at 90 feet per minute, so a 1000 ft magazine lasts just over 11 minutes, while 16 mm runs at 36 feet per minute and a 400 ft roll gives about 11 minutes too. Shooting at higher frame rates for slow motion burns film proportionally faster: the same 400 ft of 16 mm lasts only about 4.4 minutes at 60 fps.
Use this calculator to budget stock for a shoot, check how long a reel of old home movies runs, or plan scans and transfers. Enter whichever you know – length, frames or running time – and get the other two plus the number of rolls needed.
How to use the Film Footage Calculator
- Film format
- Frame rate (fps)
- I know the
- Film length
- Number of frames
- Running time
Results update as you type, every field has its own unit menu, and everything is calculated in your browser.
How it works
Choose the film format (which sets frames per foot), the frame rate and the value you know. Everything is converted to a number of frames first; the length and running time follow by dividing by frames per foot and by the frame rate.
Worked example
A 1000 ft magazine of 35 mm 3-perf film shot at 24 fps holds 1000 × 21⅓ = 21,333 frames. Running time = 21,333 ÷ 24 = 888.9 s, about 14 minutes 49 seconds. A 20-minute short needs 20 × 60 × 24 = 28,800 frames = 1,350 ft, so two 1000 ft rolls (or four 400 ft rolls).
Film formats at 24 fps
| Format | Frames per foot | Feet per minute | 400 ft lasts |
|---|---|---|---|
| 8 mm | 80 | 18 | 22 min 13 s |
| Super 8 | 72 | 20 | 20 min |
| 16 mm | 40 | 36 | 11 min 7 s |
| 35 mm 3-perf | 21⅓ | 67.5 | 5 min 56 s |
| 35 mm 4-perf | 16 | 90 | 4 min 27 s |
| 65 mm 5-perf | 12.8 | 112.5 | 3 min 33 s |
Inputs explained
| Field | What to enter |
|---|---|
| Film format | Choose one: 8 mm (Regular / Double 8) – 80 frames/ft, Super 8 – 72 frames/ft, 16 mm and Super 16 – 40 frames/ft, 35 mm 2-perf – 32 frames/ft … |
| Frame rate (fps) | A number |
| I know the | Choose one: Film length, Number of frames, Running time |
| Film length | Units: ft, m |
| Number of frames | A number |
| Running time | Units: min, s, h |
What each result means
- Running time = [Number of frames]÷[Frame rate (fps)]
- Film length = [Number of frames]÷[Film format]×0.3048
- Film length = [Number of frames]÷[Film format]×0.3048
- Film used per minute = [Frame rate (fps)]×60÷[Film format]×0.3048
- Feet per second = [Frame rate (fps)]÷[Film format]
- 100 ft rolls (daylight spools) needed = ceil([Number of frames]÷[Film format]÷100 – 1e-9)
- 400 ft rolls needed = ceil([Number of frames]÷[Film format]÷400 – 1e-9)
- 1000 ft rolls needed = ceil([Number of frames]÷[Film format]÷1000 – 1e-9)
- Running time of one 400 ft roll = 400×[Film format]÷[Frame rate (fps)]
- Running time of one 1000 ft roll = 1000×[Film format]÷[Frame rate (fps)]
Formula
Frames = length (ft) × frames per foot · Running time (s) = frames ÷ fps · Feet per minute = fps × 60 ÷ frames per foot · Rolls = ⌈length ÷ roll length⌉
Worked example
Inputs — Film format: 16 mm and Super 16 – 40 frames/ft; Frame rate (fps): 24; I know the: Film length; Film length: 400 ft.
Results — Number of frames = 16,000; Running time = 11:07; Film used per minute = 36 ft; Feet per second = 0.6 ft/s; 100 ft rolls (daylight spools) needed = 4; 400 ft rolls needed = 1; 1000 ft rolls needed = 1; Running time of one 400 ft roll = 11:07; Running time of one 1000 ft roll = 27:47.
Key terms
- Frames per foot
- How many frames fit in one foot of film, set by the gauge and pull-down.
- Perforation (perf)
- The sprocket holes along the film; the pull-down is the number of perfs per frame.
- Frame rate
- Frames exposed or projected per second – 24 fps for cinema, 25 fps for PAL television.
Frequently asked questions
How long is 400 ft of 16 mm film?
At 24 fps, 400 × 40 ÷ 24 = 666.7 s, about 11 minutes 7 seconds. At 25 fps it is 10 minutes 40 seconds.
How long does a 1000 ft roll of 35 mm last?
At 24 fps, 4-perf 35 mm runs 90 ft per minute, so 1000 ft lasts 11 minutes 7 seconds; 3-perf stretches it to 14 minutes 49 seconds.
How much film is a 90-minute feature?
129,600 frames at 24 fps – 8,100 ft of 4-perf 35 mm, or about 2,470 m.
How long is a Super 8 cartridge?
A 50 ft cartridge holds 3,600 frames: 3 min 20 s at 18 fps or 2 min 30 s at 24 fps.
What is 3-perf 35 mm?
A pull-down of three perforations per frame instead of four. It suits 16:9 framing and saves 25% of the film stock.
Do metres and feet give different frame counts?
No – the frame count depends on the physical length. One foot is 0.3048 m, so 16 frames per foot is 52.5 frames per metre.