How to Use the Slow-Motion Time Stretch Calculator

1. Pick a mode: “From Frame Rates” if you already know your capture and playback fps, or “Solve for Capture FPS” if you know the slowdown you want and need to work backward.
2. Enter your capture frame rate (or, in solve mode, your desired slowdown factor) using a quick-pick chip or by typing it directly.
3. Enter your playback frame rate — the fps of your timeline or delivery format (24, 25, 30, and 60 are the most common).
4. Enter the real-world duration of the action you’re capturing, in seconds or minutes.
5. Read the results instantly: slowdown factor, playback duration, total frames captured, recommended shutter speed, and (if you add a bitrate) an estimated file size for the capture.

Tip: capture at 240 fps and play back at 30 fps and you get an 8× slowdown — five real seconds stretches into forty seconds of footage. Higher capture rates (480, 960, 1000+ fps) push into specialty high-speed territory and need considerably more light and a camera built for it.

Mastering Slow-Motion & Frame Rate Time Stretching

Slow motion isn’t created in an edit — it’s created at the moment of capture. Every slow-mo shot is really a mismatch between two numbers: the frame rate the camera recorded at, and the frame rate the footage plays back at. Record more frames per second than you play back, and time stretches out. The bigger the gap between those two numbers, the more dramatic the stretch.

Capture FPS vs. Playback FPS

Capture frame rate is how many frames per second the sensor actually records. Playback frame rate is how many of those frames get shown per second in the final edit. The ratio between them — capture ÷ playback — is the slowdown factor. Shoot 60 fps and deliver at 24 fps, and you get a mild 2.5× slowdown, useful for smoothing out a walk or a gesture without making it look unnatural. Shoot 1000 fps and deliver at 24 fps, and you get a 41.7× slowdown — the kind of shot that turns a balloon popping into a five-second sequence of skin rippling outward.

The 180° Shutter Rule at High Speed

The same 180° rule that governs normal-speed video also applies to high-speed capture: shutter speed should be roughly 1 ÷ (2 × capture fps) to keep motion blur looking natural rather than either strobe-sharp or smeared. At 240 fps that’s about 1/480s; at 1000 fps it’s about 1/2000s. Faster shutter speeds mean less light hits the sensor per frame, which is why high-speed work almost always demands more light — bright sun, powerful continuous lighting, or a wide-open aperture — just to expose properly.

What Limits How Fast You Can Go

• Light: shorter shutter speeds at high fps need much more light than standard-speed shooting.
• Rolling shutter: many sensors read line-by-line rather than all at once; at very high frame rates this usually improves, but at lower-cost cameras pushed to their limits it can distort fast-moving subjects.
• Resolution trade-off: most cameras drop resolution or crop the sensor as frame rate climbs — 1000 fps modes are frequently 720p or smaller.
• Storage & heat: high frame rates mean far more frames per second of real time, which means larger files and more sensor heat over a session — check the file size estimate above before a long capture.

This calculator is especially useful for:

• Cinematographers planning high-speed shots on specialized cameras.
• Music video directors timing a stylized slow-motion beat drop.
• Sports and action shooters analyzing fast movement frame by frame.
• Content creators planning slow-motion for TikTok, YouTube, or Reels.

Whether you already know your camera’s frame rate options or you’re working backward from a slowdown you have in mind, this tool turns the guesswork into a straightforward shot list before you start rolling.