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Video Bitrate Explained: Mbps, Quality, and File Size

Bitrate is the number of bits an encoder spends per second, and it is the input that decides file size. This guide explains what it measures, converts it to storage, and works backwards from a size budget to a bitrate.

Published 2026-08-11 · Updated date pending

The short answer

Bitrate is how many bits of data an encoder spends on each second of video. It is written in megabits per second, Mbps. It is the number that decides file size, and it is the number platforms publish recommendations for, because resolution on its own tells an encoder nothing about how much detail to preserve.

To turn a bitrate into storage, multiply by duration and divide by eight. To go the other way — from a size budget to a bitrate — the Video Bitrate Calculator does the division for you.

What a bitrate actually measures

A bitrate is a rate, in the ordinary sense: a quantity per unit of time. Ten megabits per second means the encoder produces ten million bits for every second of running time. NIST’s note on SI and binary prefixes fixes the two conversions that follow from that: mega means 10^6, so 10 Mbps is exactly 10,000,000 bits per second, and one byte is eight bits, so those ten million bits are 1,250,000 bytes.

Bitrate is not a quality setting, though the two are related. It is a budget. A higher budget lets an encoder keep detail it would otherwise discard; it does not oblige it to. Give an encoder 50 Mbps for a static slate and most of the budget goes unspent.

Nor is bitrate a property of resolution. The same 1920x1080 frame can be encoded at 2 Mbps or 50 Mbps. Both are 1080p. This is why every platform bitrate table is a recommendation attached to a resolution rather than a fact derived from one.

Mbps to megabytes: the conversion in full

totalBitrate  = videoBitrate + audioBitrate
payloadBits   = totalBitrate x durationSeconds
fileSizeBytes = payloadBits / 8

Applying it to ten minutes at 12 Mbps of video and 128 Kbps of audio:

totalBitrate  = 12 000 000 + 128 000 = 12 128 000 bps
payloadBits   = 12 128 000 x 600     = 7 276 800 000 bits
fileSizeBytes = 7 276 800 000 / 8    =   909 600 000 bytes
              = 909.60 MB

The division by eight is the step people skip. A 20 Mbps connection moves 2,500,000 bytes per second, not 20,000,000. The same factor of eight separates Mbps from MB/s everywhere it appears, and Mbps vs MB/s is entirely about the mistakes it causes.

Working backwards from a size budget

The more useful direction is usually the reverse: you have a size limit and need a bitrate that fits inside it. Rearranging the same equation:

payloadBytes    = targetBytes / (1 + overheadFraction)
payloadBits     = payloadBytes x 8
totalBitrate    = payloadBits / durationSeconds
videoBitrate    = totalBitrate - audioBitrate

For a 1 GB target, a ten-minute runtime and a 128 Kbps audio track, with overhead left at zero:

targetBytes  = 1 000 000 000 bytes
payloadBits  = 1 000 000 000 x 8   = 8 000 000 000 bits
totalBitrate = 8 000 000 000 / 600 = 13 333 333.333... bps
videoBitrate = 13 333 333.333... - 128 000
             = 13 205 333.333... bps
             = 13.205 Mbps

The audio track is about 1.0% of the total here. Enter the same three values in the Video Bitrate Calculator and it returns 13.205 Mbps. Note that the audio bitrate is subtracted, not ignored: if the audio track alone exceeded the budget the calculator reports that rather than returning a negative video bitrate.

Per minute and per hour: the numbers worth memorising

Most planning happens in minutes and hours rather than in single clips, and the conversion is small enough to keep in your head. A bitrate in Mbps becomes megabytes per minute by multiplying by 60 and dividing by 8 — that is, by multiplying by 7.5:

Video bitrate Per minute Per hour
8 Mbps 60 MB 3.60 GB
12 Mbps 90 MB 5.40 GB
16 Mbps 120 MB 7.20 GB
35 Mbps 262.5 MB 15.75 GB
100 Mbps 750 MB 45.00 GB

Those figures exclude audio. Add a 384 Kbps stereo track and each row rises by 2.88 MB per minute. The point of the table is not the individual numbers but the shape: the relationship is linear in both bitrate and duration, so doubling either doubles the result, and there is never a threshold or a surprise in between.

Why platforms publish bitrate tables

Two platforms publish recommendations that make the point plainly.

YouTube’s recommended upload encoding settings give a bitrate per resolution and frame rate — for example 8 Mbps for 1080p at 24, 25 or 30 fps, rising to 12 Mbps at 48, 50 or 60 fps — and recommend the MP4 container with the H.264 video codec and 384 kbps stereo audio.

Vimeo’s compression guidelines give ranges instead: 10–20 Mbps for 1080p, 20–30 Mbps for 2K, and 30–60 Mbps for 4K, with AAC-LC audio at 48 kHz and 320 kb/s CBR.

The two sets of numbers disagree, and that disagreement is informative. These are each platform’s advice about what its own transcoder wants to receive, not a measurement of what a given resolution requires. Take the recommendation from the platform you are delivering to.

Bitrate, codecs, and what the specification does and does not say

H.264 is published by the ITU-T as Recommendation H.264, “Advanced video coding for generic audiovisual services”, and remains in force. The specification defines how a conforming bitstream is written and decoded. It does not prescribe a bitrate: the same specification covers a 500 Kbps stream and a 200 Mbps one.

That separation matters when comparing codecs. A newer codec is generally used at a lower bitrate for comparable output, but this site publishes no efficiency ratio, because a ratio depends on content, encoder, settings and the judgement of whoever looked at the result. H.264 vs H.265 covers what can and cannot be said about the pair.

What this does not tell you

  • Bitrate does not guarantee quality. It sets an upper bound on how much information can be retained. A poorly configured encoder can waste a generous budget.
  • The size arithmetic assumes the stated bitrate is the achieved average. With variable bitrate the encoder aims at an average and varies around it. See CBR vs VBR.
  • Platform tables are advice, not limits. They describe what a platform prefers to receive. They change, and the access date on every figure above is the date it was checked.
  • Container overhead is excluded. The calculator defaults the overhead field to zero, giving the raw payload.

Frequently asked questions

Is a higher bitrate always better?

No. Above the point where the encoder can already represent the source, extra bitrate produces a larger file and no visible change. Where that point falls depends on the footage. The practical approach is to start from the recommendation published by your delivery platform.

How do I convert Mbps to MB per minute?

Multiply by 60 to get bits per minute, then divide by 8. At 12 Mbps that is 12,000,000 x 60 / 8 = 90,000,000 bytes, or 90 MB per minute.

Does audio bitrate matter?

It matters most when the video bitrate is low. At 12 Mbps of video a 128 Kbps audio track is about 1% of the total. At 1 Mbps of video the same track is over 11%. The calculator lets you set it or switch it off.

What bitrate should I export at?

Whatever your delivery target publishes. YouTube and Vimeo both publish tables, and they do not agree with each other, which is why this site links to them rather than inventing a third set. Best bitrate for 1080p, 1440p and 4K video sets them side by side.

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