Video timing
Frames to time calculator
Divide the number of frames by the capture frame rate to get elapsed time. 18 frames at 240 fps is 0.075 seconds (75 ms); the same 18 frames at 60 fps is 0.300 seconds. The frame rate also sets your precision: each frame is about 4.2 ms at 240 fps and 16.7 ms at 60 fps.
The rate the video was captured at, not the playback rate. iPhone slow motion is 120 or 240 fps.
From “Start event” to “End event”. Use the end frame number minus the start frame number.
Elapsed time
0.200s
- Frames counted
- 48
- One frame lasts
- 4.2 ms
How to time a movement from video
- Decide exactly which visible moment starts the interval and which ends it, such as the first frame of foot contact and the first frame the foot leaves the ground.
- Step frame by frame to the start frame, then step forward to the end frame, counting the frames in between.
- Enter the frame count and the frame rate the video was captured at.
Formula
time = frames ÷ fps
Precision is plus or minus one frame, which is 1 ÷ fps seconds. An event that happens between two frames can appear up to one frame early or late.
Times in frames at common frame rates
| Time | Frames at 30 fps | Frames at 60 fps | Frames at 120 fps | Frames at 240 fps |
|---|---|---|---|---|
| 0.10 s | 3 | 6 | 12 | 24 |
| 0.20 s | 6 | 12 | 24 | 48 |
| 0.25 s | 8 | 15 | 30 | 60 |
| 0.50 s | 15 | 30 | 60 | 120 |
| 1.00 s | 30 | 60 | 120 | 240 |
| 2.00 s | 60 | 120 | 240 | 480 |
Common mistakes
- Using the playback frame rate. A 240 fps slow-motion clip plays back at 30 fps, so one real second takes eight seconds on screen.
- Off-by-one counting. Count the steps between frames (end frame minus start frame), not the number of frames including both ends.
- Timing edited, exported, or screen-recorded clips. These can be re-timed or drop frames; time the original recording whenever possible.
- Changing the event definition between athletes or sessions, which makes comparisons meaningless.
Frequently asked questions
How many milliseconds is one frame of video?
About 33.3 ms at 30 fps, 16.7 ms at 60 fps, 8.3 ms at 120 fps, and 4.2 ms at 240 fps.
Is counting frames more accurate than a stopwatch?
At 120 fps and above, frame counting is usually more precise than hand timing because it removes the timer's reaction time. Its precision is limited by the frame rate rather than by reflexes.
What does 240 fps slow motion mean for timing?
The camera captures 240 frames every second and plays them back at 30 fps, so motion appears eight times slower. For timing, always divide by the 240 capture rate.
Related terms
Count frames on your iPhone or iPad
KineVision plays video in slow motion, steps through it frame by frame, and includes a stopwatch, angle tools, and side-by-side comparison for coaching.
Download on the App StoreMore tools
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