Frame rates explained: why video uses 24, 25, 30, 60 and 29.97 fps

Frame rate is the number of still images shown per second of video. The common rates are not arbitrary: 24 fps comes from cinema, 25 and 50 from television in countries with 50 Hz mains electricity, and 30, 60 and the odd-looking 29.97 from American television. Knowing why helps you pick the right one, and video info tells you what any MP4 or MOV file actually uses.

What frame rate means

Video is a sequence of still frames; shown quickly enough, the brain reads them as continuous motion. Around 24 frames per second motion looks convincingly smooth, especially with the natural motion blur a camera records. Higher rates look smoother and sharper in movement; lower rates look jerky. Frame rate also affects file size, since more frames mean more data, and exposure, since each frame can be exposed for at most the interval between frames. Filmmakers often use the 180-degree shutter rule, an exposure of about 1/(2 × frame rate), such as 1/50 second at 24 or 25 fps, to get familiar-looking motion blur.

24 fps: the film standard

Silent films were shot and projected at varying speeds, often well below 24 fps. When sound arrived in the late 1920s, the optical soundtrack running alongside the pictures needed a constant, fast enough speed for decent audio, and 24 fps became the standard: fast enough for sound and smooth motion, slow enough to keep film stock affordable. It stuck. Most cinema is still made at 24 fps, and the look of 24 fps motion blur is now part of what audiences read as cinematic.

25 and 50: PAL regions

Early television tied its timing to mains electricity to avoid visible interference. In Europe, much of Asia, Africa and Australia mains runs at 50 Hz, so television ran at 50 interlaced fields per second, each carrying half the lines, giving 25 full frames per second. That became the PAL and SECAM world of 25 and 50 fps. Films shown on 25 fps television are simply run 4 per cent fast: a two-hour film lasts 115.2 minutes, and the sound rises by about 0.7 of a semitone unless it is corrected.

30, 29.97 and 23.976: the NTSC legacy

In North America, 60 Hz mains led to 60 fields and 30 frames per second. When colour was added to the NTSC system in 1953, the colour signal could interfere with the sound carrier, and the fix was to slow everything by a factor of 1000/1001. So 30 fps became 30000/1001, about 29.97, and 60 became 59.94. Film transferred to that system runs at 24000/1001, about 23.976 fps, and is spread across the fields with 3:2 pulldown, which maps every 4 film frames onto 10 video fields. The fractional rate makes clocks drift: counting 30 frames a second, an hour of 29.97 fps video falls short by about 108 frames, or 3.6 seconds. Drop-frame timecode fixes that by skipping frame numbers 00 and 01 at the start of every minute except each tenth minute, which removes exactly 108 numbers an hour. Digital cameras still offer 23.976, 29.97 and 59.94 for compatibility with that world.

50, 60 and higher

Rates of 50 and 60 fps capture fast motion more clearly, which is why sport, video games and screen recordings use them. Some viewers find high frame rates too smooth for drama; when The Hobbit was released at 48 fps in 2012, many critics said it looked like video rather than film. Phones also record at 120 or 240 fps for slow motion: played back at 30 fps, 120 fps footage is four times slower and 240 fps eight times slower. The video speed tool changes playback speed after the fact, though it cannot create frames that were never recorded.

Choosing and checking a frame rate

• Match the lights. Under mains-powered lighting, shoot 25 or 50 fps in 50 Hz countries and 30 or 60 in 60 Hz countries to avoid flicker and banding.
• Match the destination. Use 24 or 23.976 for a cinematic look, 25 or 29.97 to match broadcast in your region, and 50 or 60 for fast motion.
• Don't mix rates in one edit. Converting 30 fps to 25 drops or blends frames and can make motion judder.

Video info calculates the rate from the file's own frame table, frames divided by duration, so it shows 29.97 rather than a rounded 30. Many phones record variable frame rate, so the figure for phone video is an average. To inspect individual frames, the frame extractor saves stills. GIFs have their own timing rules, explained in How GIF frame timing works: delays, speed and loop counts.