Frame Rates Explained: 24, 25, 30, 50 and 60 fps, and Why the UK Uses 25/50

Frame rate is simply how many still images (frames) a video shows per second. In the UK, the sensible default for most creator work is 25 fps, or 50 fps for fast motion, because our mains electricity runs at 50 Hz and our broadcast system grew up around it. The numbers you choose matter less than keeping them consistent from camera to timeline to export, because most frame-rate problems come from mixing rates rather than from picking the "wrong" one.

The common frame rates and what they are for

Higher frame rates capture motion more smoothly but look more "live" and less filmic. Lower rates give more motion blur per frame and the familiar cinema look.

Why the UK uses 25 and 50

PAL heritage

UK analogue television used the PAL colour system at 625 lines and 50 interlaced fields per second. Each field carried every other line of the picture, and two fields made one frame, so the frame rate was 25. When television went digital and then high definition, the UK kept the same timing family: HD broadcast in the UK is 1080i50 (50 interlaced fields, 25 frames) or 720p50/1080p50 for progressive high frame rate material.

That is why UK broadcasters and many UK-based clients still ask for 25 fps (often written 25p) or 50 fps. If you ever deliver to a UK broadcaster, their technical specification will name the exact rate, and you should follow it rather than a general guide.

50 Hz mains and lighting flicker

The more practical reason for UK creators is lighting. Mains electricity in the UK alternates at 50 Hz, and many lights (older fluorescent tubes, cheap LED bulbs and some LED panels) pulse in brightness at twice that frequency: 100 times per second. You do not see it with your eyes, but a camera can.

If your shutter speed does not line up with that pulse, you get flicker or rolling dark bands across the frame. The classic mistake is shooting 30 fps with a 1/60 s shutter indoors in the UK: 1/60 s does not contain a whole number of 1/100 s light cycles, so each frame catches a slightly different amount of light.

Shutter speeds that divide cleanly into the UK's 100 Hz flicker include:

• 1/50 s (two full cycles of the 100 Hz pulse)
• 1/100 s (one full cycle)
• 1/25 s (four cycles, only usable at 25 fps and below)

This is why 25 fps with a 1/50 s shutter (the "180-degree shutter" rule: shutter speed roughly double the frame rate) is the UK default. At 50 fps, 1/100 s works cleanly. If you must shoot 30 or 60 fps under UK mains lighting, look for a camera setting labelled "flicker reduction", "anti-flicker" or a fine-grained shutter setting, or light the scene with good-quality flicker-free LED fixtures.

Daylight and battery-powered LED panels designed for video generally do not flicker, so outdoor footage is far less fussy.

Where 23.976 and 29.97 come from

These odd numbers are a leftover from US colour television. When colour was added to the North American NTSC system in the 1950s, engineers slowed the frame rate by a factor of 1000/1001 to avoid interference between the new colour signal and the sound carrier. 30 fps became 30000/1001, which is roughly 29.97 fps.

Film shot at 24 fps then had to be converted for that system, so it was slowed by the same ratio to 24000/1001, roughly 23.976 fps, and spread across 29.97 video frames using a pattern called 3:2 pulldown.

In practice, today:

• Many phones and cameras sold worldwide default to 29.97 or 30 fps, even in the UK. Check the setting before you shoot.
• "24p" on a camera menu may actually mean 23.976. Most cameras label both separately if they offer both.
• ffprobe shows the exact rate as a fraction, such as 30000/1001:

ffprobe -v error -select_streams v:0 -show_entries stream=r_frame_rate,avg_frame_rate -of default=nw=1 clip.mp4

If r_frame_rate and avg_frame_rate differ noticeably, the clip is probably variable frame rate (common with phone and screen recordings), which we cover below.

What goes wrong when you mix frame rates

Judder from frame duplication

Drop a 25 fps clip into a 30 fps timeline and the editor has to invent five extra frames every second, usually by repeating existing ones. Every fifth frame is shown twice, which produces a regular stutter on pans and moving subjects. Going the other way (30 into 25) drops frames and gives a similar, slightly jerky feel.

Frame blending or optical-flow retiming can smooth this, but may add ghosting around fast motion.

The PAL speed-up

The traditional way to put 24 fps film onto UK television was not to add frames but to play it 4% faster at 25 fps. A 100-minute film ran in about 96 minutes, and audio rose in pitch by roughly 0.7 of a semitone unless it was corrected. You can do the same in your editor by "conforming" 24 fps footage to 25 fps: motion stays perfectly smooth, but the clip gets shorter and any sound on it must be pitch-corrected or replaced.

Audio and caption drift

If a clip is conformed to a different rate but its audio or captions are not adjusted by the same ratio, sync drifts steadily over time. The same happens when 29.97 and 30 fps are confused: the 0.1% difference is about 3.6 seconds per hour, easily enough to push captions visibly late by the end of a long video. Our guide on fixing subtitle sync drift explains how to spot a constant ratio error and correct it, and the SRT shifter tool can apply the correction in your browser.

Variable frame rate recordings

Phones and screen recorders often record variable frame rate (VFR) to save power. Some editors handle VFR badly, producing audio that slowly slips out of sync. Converting to a constant rate before editing avoids the problem:

ffmpeg -i phone_clip.mp4 -vf fps=25 -c:v libx264 -crf 18 -preset medium -c:a aac -b:a 192k phone_clip_25p.mp4

The fps filter drops or duplicates frames as needed to hit exactly 25 fps. More commands like this are in our FFmpeg commands for creators guide, and the official filter documentation is at >ffmpeg.org.

AI-generated clips

Many AI video generators output 24 fps. If your edit is 25 fps, you will either get a duplicated frame every second or need to conform the clips to 25 (which speeds them up by about 4%). For silent AI clips, conforming is usually the cleaner choice, because there is no audio to pitch-shift and motion stays smooth. Stills animated with a Ken Burns move have no native rate at all, so render them at whatever your timeline uses.

Choosing a frame rate for your project

A simple decision process for UK creators:

1. Talking heads, explainers, vlogs shot indoors in the UK: 25 fps, 1/50 s shutter.
2. Sport, gaming, fast action or anything you may slow down: 50 fps, 1/100 s shutter. Footage shot at 50 can be played at 25 for clean 2x slow motion.
3. Film-look drama or music videos: 24 fps is fine, but watch for indoor flicker and set the shutter to 1/50 s where the camera allows it.
4. Screen recordings and gameplay: match the source. If the game runs at 60, record 60 and edit at 60.
5. Working with a US client or US-shot footage: ask whether they want 23.976, 29.97 or 59.94, and edit the whole project at that rate.

YouTube accepts all the common rates. At the time of writing, its help page "Recommended upload encoding settings" lists 24, 25, 30, 48, 50 and 60 fps and advises uploading at the same frame rate you recorded in. See the >official YouTube Help page and our YouTube export settings guide for the rest of the export recipe.

Quick checklist

• Decide the project frame rate before you shoot, and write it in the project notes.
• Set every camera and phone to that rate; check that "24" does not secretly mean 23.976 or vice versa.
• Indoors in the UK, use a 1/50 or 1/100 s shutter to avoid mains flicker.
• Convert variable frame rate phone and screen recordings to a constant rate before editing.
• Set the timeline to the project rate and let odd clips conform or retime to it, never the reverse.
• Export at the timeline rate; do not change frame rate at the final export.
• If you conform footage with audio, pitch-correct or replace the audio and re-time captions by the same ratio.

FAQ

Is 25 fps worse than 30 fps for YouTube?

No. Viewers cannot tell 25 from 30 in normal content, and YouTube plays both natively. What matters is that your footage is shot and exported at one consistent rate. In the UK, 25 fps is often the safer choice because it avoids mains lighting flicker.

Why does my indoor footage have rolling dark bands?

Almost always a mismatch between your shutter speed and 50 Hz mains lighting. Switch to a 1/50 or 1/100 s shutter, turn on the camera's anti-flicker setting, or use flicker-free video lights.

Can I convert 50 fps footage to 25 fps without losing quality?

Yes. Dropping every other frame is a clean conversion with no judder, because 50 divides exactly by 2. Alternatively, keep all 50 frames and play them at 25 fps for smooth half-speed slow motion.

Should I use drop-frame timecode?

Drop-frame timecode only applies to 29.97 and 59.94 fps, and it exists so the timecode clock matches real elapsed time. It does not drop any actual frames. For 25 and 50 fps projects in the UK, it is not relevant.