Slow Motion Pacing Calculator

Slow motion is a ratio of frame rates. Ten seconds at 120 fps played at 24 fps is 50 seconds on the timeline — a 5× slow-mo. Time the action with a phone stopwatch, then check you have card and light for the shoot fps. A test clip of a hand wave tells you if 120 is enough or you need 240.

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Playback duration: 50.00s
Slow-motion factor: 5.00×

Recommended gear

CFexpress card
High fps is a bitrate spike. A slow card drops frames and the slow-mo stutters.
Typical range: $80–$250
Gimbal stabilizer
Slow-mo walk-and-talks show every footstep. A gimbal or a locked-off stick is cleaner than IBIS alone at 1/240.
Typical range: $200–$700
Field monitor
Confirm the high-speed crop and rolling shutter on a monitor before the jump, not in the edit.
Typical range: $200–$800

Calculation method

Playback time is record time multiplied by shoot fps over playback fps. The slow-motion factor is that same ratio. 120/24 is 5×, so a 10 s take becomes 50 s. If you record 24 fps and play 24 fps, the factor is 1 — realtime. Speeding up is a factor under 1 (shoot 24, play 60).

Exact formula

playbackSeconds = recordSeconds × (shootFps / playbackFps). slowMoFactor = shootFps / playbackFps. Limits: Rolling shutter, light loss, audio stretch and variable-frame ingest omitted.

How much slow-mo is enough

2× (48 fps to 24) is a gentle dream. 5× (120 to 24) is a splash or a jump. 10× (240 to 24) is a science clip. Time the action; do not pick 240 because it sounds pro.

Offspeed 24

Shooting 30 fps for a 24 fps timeline is a 1.25× slow. Some people use it as a subtle fattening of motion. Same formula.

Frequently asked questions

Audio?

Most bodies drop audio, or it will pitch down. Plan MOS or replace in the edit. This calculator does not stretch waveforms.

Shutter at 120 fps?

Keep ~180°: 1/240 s. That is two stops darker than 1/60. Budget ISO, aperture or light before you call 120 ‘free’.

Cropped 120 fps?

Many cameras crop or drop to 8-bit. Check the manual. The pacing math does not change; the field of view does.

Disclaimer — no professional advice, no liability

This is pacing math, not a promise your body can hold 120 fps in that codec. Rolling shutter on a fast pan will still jello. Record a test clip at the taking fps before the stunt.

These calculators, pages and any related content are provided “as is” and “as available”, solely for general educational and informational purposes. They are simplified mathematical estimates, not a light-meter reading, a studio plot or a shooting prescription, and they do not constitute professional photographic, cinematographic or optical advice.

Results can be wrong, incomplete or inapplicable to your camera, lens, sensor, filter, lighting or use case. You must independently verify every figure, assume all risk, and confirm settings on a test shot before a job that can miss the image, damage gear or injure someone.

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Slow Motion Pacing Calculator

Inputs

Results

Recommended gear

Calculation method

Exact formula

How much slow-mo is enough

Offspeed 24

Frequently asked questions

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