Video File Size Calculator
Estimate the file size of a video from its bitrate and duration, or work backwards from a size limit to the bitrate you can afford.
What the encoder was set to for the picture.
Set to 0 if the video has no sound.
Estimated file size
581.4 MB
8.13 Mbps combined for 10:00. Container overhead adds roughly half a percent on top, so treat this as a close floor rather than an exact figure.
Per minute
58.1 MB
Per hour
3.41 GB
Exact bytes
609,600,000
Only use A2Z Video Tools with content you own, content in the public domain, or content you have permission to download, save, convert or use. Users are responsible for complying with applicable laws and the terms of the source platform.
How the figure is worked out
A video file is, at heart, a stream of bits arriving at a steady rate. Multiply that rate by how long it runs and you have the size. That is the whole calculation:
size in bytes = (video kbps + audio kbps) × 1000 × seconds ÷ 8
The division by eight converts bits to bytes. The multiplication by a thousand is where most confusion starts, so it is worth stating plainly: in bitrates, kilo means exactly one thousand. In file sizes, a megabyte usually means 1,048,576 bytes. The two conventions disagree by about five per cent, which is why a file that should come in at 25MB sometimes shows as 23.8MB in a file manager. This tool uses each convention where it belongs and labels both.
Why the real file is slightly larger
The estimate above counts the audio and video streams. A finished file also carries a container around them, which stores an index of where every frame sits, plus any subtitles, chapter markers and metadata. For a normal MP4 this adds roughly half a percent. On a very short clip it is negligible. On an hour-long file it can be a few megabytes, which matters when you are trying to land just under a hard limit.
Treat the number as a close floor. If you are aiming at a strict cap, aim a couple of per cent under it.
Variable bitrate
Most modern encodes are not a constant rate. The encoder spends more bits on a busy scene and fewer on a static one, which is why quality holds up better at the same average. When an encoder is set to a target average bitrate, this calculation still predicts the final size well. When it is set to a quality level instead, such as a constant quality factor, the encoder decides the bitrate itself and the size cannot be predicted in advance at all. You get the quality you asked for and find out the size afterwards.
A worked example
A ten minute clip at 8,000 kbps video and 128 kbps audio comes to 8,128 kbps over 600 seconds. That is 4,876,800,000 bits, or 609,600,000 bytes, which a file manager will show as about 581MB. Halving the video bitrate roughly halves the file, because the audio is a small part of the total.