Video Bitrate & File Size Calculator
Calculate video bitrate, file size, or recording time from the other two. Free bitrate calculator with container overhead guidance. No file needed.
What this tool does
This bitrate calculator turns a target into numbers you can set in an encoder: enter any two of bitrate, file size, and duration, and it gives you the third. It runs in the browser, needs no file, and takes seconds.
Use it before an export to hit an upload limit, before a recording to plan storage, or to check that a delivery spec is realistic for your footage.
How it works
- Choose what you want to find: bitrate, file size, or duration.
- Enter the values you already know.
- The answer appears instantly, with headroom guidance for container overhead.
Supported formats
No file input: everything runs in your browser. Nothing is uploaded.
When to use it
Hit an upload limit
Work backwards from a size cap to the bitrate that fits it, before you waste an export. Once the number is set, the Video Compressor can act on it and produce a file at that size.
Plan a recording
Convert a card or drive capacity into minutes of footage at a given quality.
Set export settings
Translate a target file size into a bitrate your editor will accept.
Check a delivery spec
Confirm a requested size is realistic for the duration before committing to it.
The math, done for you
Bitrate, file size, and duration are three sides of one equation: size equals bitrate multiplied by time. Fix any two and the third is determined. The calculator does that arithmetic instantly and adds the container overhead guidance that raw math leaves out.
The results are planning numbers. Real encoders vary: motion, scene cuts, and codec settings all push the final file a few percent away from the prediction. The tool says so directly rather than implying false precision, and the headroom note absorbs most of the variance.
No file is needed and nothing is uploaded. It is a calculator that runs in the browser, in the same spirit as the rest of this site.
Here is a worked example: a 10 minute video at 10 Mbps video plus 128 kbps audio. Combined bitrate 10128 kbps, so 10128 × 1000 × 600 seconds ÷ 8 = 759,600,000 bytes, which is 759.6 MB. The calculator runs exactly this arithmetic; change any input and the result follows the same relation.
Rough starting bitrates by resolution, H.264 first and H.265 second, which needs about 40 percent fewer bits for the same look. Treat each range as a starting point, not a rule:
720p: H.264 2.5 to 5.5 Mbps, H.265 1.5 to 3.5 Mbps.
1080p: H.264 5 to 12.5 Mbps, H.265 3 to 7.5 Mbps.
1440p: H.264 9 to 21 Mbps, H.265 5.5 to 12.5 Mbps.
4K: H.264 17 to 42 Mbps, H.265 10 to 25 Mbps.
Frequently asked questions
Why did my exported file end up bigger than the calculation?
Container overhead plus how the encoder spends its bits: audio adds its own track, and complex scenes get more data than the average. Leave the suggested headroom and you land within a few percent. Exact sizing is an encoder feature, not a math feature.
How accurate is it?
The arithmetic is exact; the prediction is not, because real encoders are not constant-rate machines. Treat the result as a target, not a guarantee, and use the headroom note when a cap is involved.
What bitrate should I use for YouTube?
Check the platform requirements with the Video Compatibility Checker, then come back here to see what file size that bitrate produces for your duration.
Does it work for audio files?
Yes. The same size-equals-bitrate-times-time relation holds for audio; enter the audio bitrate and duration and the calculator does the rest.
What is the difference between MB and MiB?
A megabyte (MB) is 1,000,000 bytes; a mebibyte (MiB) is 1,048,576 bytes. Upload limits and storage marketing use decimal MB, while many operating systems report sizes in binary MiB, so the same file can look about 5 percent bigger in one place than another. The calculator shows both numbers side by side so you can compare against either kind of limit.
Does resolution or frame rate change the file size?
Not directly. Bitrate alone determines size. Resolution and frame rate matter because higher values usually need more bitrate to look good, so in practice a 4K export is larger than a 1080p one. At a fixed bitrate, though, a 1080p and a 4K export of the same duration come out nearly the same size; the 4K version just spreads those bits thinner and looks softer. For starting bitrates by resolution and codec, and what audio and HDR add on top, see the video file size guide.
What is the difference between constant and variable bitrate?
Constant bitrate (CBR) spends the same number of bits every second, which makes file size math exact but wastes bits on easy scenes. Variable bitrate (VBR) spends more on complex scenes and less on static ones, so quality per byte is better, but the final size lands near the target rather than exactly on it. Use CBR when a size cap is hard, VBR when quality matters most.
What audio bitrate should I use?
128 kbps AAC or MP3 is fine for voice and general content; 192 to 256 kbps suits music-heavy material. Audio is small compared to video, so it barely moves the total. If your file has several audio tracks, the track count multiplies that cost, which is why the calculator asks for it.
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