Estimate a video file's size from its bitrate and duration.
Calculator verified • Last updated: August 2026
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This estimate covers the video stream only — add your audio track's bitrate separately for a more precise total.
Bitrate measures how much data a video stream uses per second. Multiplying bitrate by the total duration in seconds gives the total data in megabits, and dividing by 8 converts that to megabytes — the standard unit file sizes are reported in.
$$\text{Size (MB)} = \frac{\text{Bitrate} \times \text{Duration} \times 60}{8}$$
Bitrate: video bitrate, in megabits per second (Mbps).
Duration: video length, in minutes (multiplied by 60 to get seconds).
A 10 Mbps video that runs for 10 minutes (600 seconds): 10 times 600 equals 6,000 megabits, divided by 8 equals 750 megabytes. A higher bitrate of 50 Mbps (common for 4K footage) over the same 10 minutes would produce 50 times 600 divided by 8, or 3,750 megabytes — about 3.66 gigabytes.
Resolution, frame rate, and codec efficiency all drive bitrate up or down independently of duration. A 4K video needs a much higher bitrate than 1080p to look equally sharp, since it has roughly four times the pixels to encode each frame; a more efficient codec (like H.265/HEVC compared to older H.264) can deliver similar visual quality at a meaningfully lower bitrate, which is why the same footage can produce very different file sizes depending on export settings.
Confusing megabits and megabytes is the most common error in this exact calculation — bitrate is almost always specified in megabits per second (Mbps), but file size is reported in megabytes (MB), and the two differ by a factor of 8. Skipping the division by 8 overstates the estimated file size eightfold.
Forgetting to convert duration from minutes to seconds before multiplying by a per-second bitrate is another — the formula above already includes the times-60 conversion, but a manual calculation done by hand often misses it.
Bitrate — the amount of data used per second of video, usually measured in megabits per second (Mbps); higher bitrate generally means higher quality and a larger file.
CBR vs. VBR — Constant Bitrate encodes every second at the same bitrate; Variable Bitrate adjusts bitrate scene by scene, using more data for complex motion and less for static scenes, often producing a smaller file at similar quality.
Codec — the compression algorithm (like H.264 or H.265) used to encode video; more efficient codecs achieve similar quality at a lower bitrate.
Multiply the bitrate (in megabits per second) by the duration in seconds, then divide by 8 to convert megabits to megabytes. A 10 Mbps video that's 10 minutes (600 seconds) long, for example, is 10 x 600 / 8, or 750 megabytes.
Use the target or actual video bitrate from your camera, encoder, or streaming platform's recommended settings — this is usually listed in the video settings menu or export/encoding dialog, separate from audio bitrate, which this calculator doesn't include.
No — this calculator estimates size from the video bitrate alone. Audio typically adds a relatively small amount on top (often 128-320 kbps, a small fraction of typical video bitrates), so for a rough estimate the video bitrate alone is usually close enough, but add the audio bitrate to the total for a more precise figure.