Shutter Angle to Speed Calculator
Cinema cameras express exposure as a shutter angle, a holdover from rotary film shutters, while still cameras use a shutter speed in seconds. This calculator converts between them: enter your shutter angle and frame rate to get the equivalent shutter speed, the exposure time as a fraction of a second, and the speed that the natural-motion 180 degree shutter would give at your frame rate. Use it to match a cinematic look or to dial in motion blur.
Shutter angle formula
Shutter speed (s) = angle / (360 * frame rate)
1/x denominator = 360 * frame rate / angle
180 degree speed = 1 / (2 * frame rate)
The shutter is open for the fraction angle / 360 of each frame interval. Dividing by the frame rate turns that into an exposure time in seconds.
Worked example
A 180 degree shutter at 24 fps: shutter speed = 180 / (360 * 24) = 180 / 8,640 = 0.0208 seconds. As a fraction that is 1/48 second. The 180 degree speed at 24 fps is 1 / (2 * 24) = 1/48 second, confirming the result.
Shutter angle: frequently asked questions
How do I convert shutter angle to shutter speed?
Shutter speed in seconds equals the shutter angle divided by (360 times the frame rate). At 24 fps with a 180 degree shutter, that is 180 / (360 * 24) = 1/48 second, the classic cinematic exposure.
What is the 180 degree shutter rule?
A 180 degree shutter exposes each frame for half the frame interval, giving motion blur that looks natural to the eye. It is the default starting point for cinematic motion; smaller angles look crisper and choppier, larger angles look more blurred and dreamy.
Why use shutter angle instead of shutter speed?
Shutter angle comes from rotary film shutters and stays constant relative to frame rate, so the motion blur look is preserved when you change frame rate. A fixed shutter speed would change the blur character as frame rate changes; the angle keeps it consistent.
Sources
- NIST: Time and Frequency Division (the second).
- Shutter speed = angle / (360 fps) follows from the rotary-shutter definition; no external figure is required.
Reviewed by the CalculatorHub team, edited by James Graham, 19 June 2026. See our methodology.