Video Bitrate File Size Calculator
Turn a bitrate and clip length into a file size, find the highest bitrate that fits a card, disc or size limit, or see how long you can record — with codec presets, audio tracks, container overhead, GiB sizes, card tables and upload time.
How it works
Total bitrate = (video Mbps + audio kbps × tracks ÷ 1,000) × (1 + overhead) · File size (GB) = total Mbps × seconds ÷ 8 ÷ 1,000 · Max video bitrate = space (GB) × 8,000 ÷ seconds ÷ (1 + overhead) − audio Mbps · Recording time = space (GB) × 8,000 ÷ total Mbps
A video file is its bitrate poured out over time. The video stream and every audio track each use a fixed number of megabits per second; add them up, multiply by the length in seconds and divide by eight to get megabytes, then by 1,000 for gigabytes. The container (MP4, MOV, MKV) adds a little for headers and the index, which you can include as a percentage. The same sum works backwards. Pick “Max bitrate” to find the highest video bitrate that still fits a card, a disc or an upload limit for a given length — the audio is taken out of the budget first. Pick “Recording time” to see how long a card lasts at the bitrate you shoot. Presets cover common streaming, phone, camera, Blu-ray and Apple ProRes rates, and the tables show the same clip at other bitrates and the recording time on standard card sizes. Card and drive sizes are decimal gigabytes; the GiB figure is what Windows reports.
Worked example
A 50 Mbps clip with 256 kbps audio for 10 minutes (600 s): total bitrate 50.256 Mbps, so 50.256 × 600 ÷ 8 ÷ 1,000 = 3.77 GB — about 377 MB per minute or 22.6 GB per hour, which Windows shows as 3.51 GiB. A 64 GB card holds 64 × 8,000 ÷ 50.256 = 10,188 s, about 2 hr 49 min, at that rate. To fit the same 10 minutes into 4.7 GB for a DVD, the video bitrate must stay below 4.7 × 8,000 ÷ 600 − 0.256 = 62.4 Mbps.
Sources: Apple ProRes white paper (data rates) · YouTube Help: recommended upload encoding settings
Frequently asked questions
Are these gigabytes or gibibytes?
The calculator uses decimal gigabytes (1 GB = 1,000,000,000 bytes), which is how cards, drives and camera specs are labelled. Windows divides by 1,024³ and still writes “GB”, so the same file looks about 7% smaller there; the GiB result shows that figure.
What bitrate should I record at?
It depends on resolution, frame rate and codec. YouTube suggests about 8 Mbps for 1080p and 35–45 Mbps for 4K uploads; cameras record 1080p at 25–50 Mbps and 4K at 100–150 Mbps in H.264/HEVC; editing codecs such as ProRes 422 HQ use 220 Mbps at 1080p and 707 Mbps in 4K. Higher bitrate keeps more detail but fills cards faster.
How long will my card last?
Choose “Recording time”, pick the card and enter the bitrate. Time = card GB × 8,000 ÷ total Mbps; a 128 GB card at 100 Mbps holds about 2 hr 50 min. The table lists every common card size at your bitrate, and you can keep a few percent free as a safety margin.
Does audio really matter to file size?
At high video bitrates it is a small share, but uncompressed audio is not small: 48 kHz 24-bit stereo is 2,304 kbps, and four tracks of it add more than 9 Mbps. At low video bitrates or for long recordings, include every track.
Why is my real file a little bigger or smaller?
Most encoders use variable bitrate, so the setting is an average, and containers add headers, an index and sometimes timecode or metadata tracks. Add 1–2% container overhead when the file must fit a hard limit such as an upload cap or a 4 GiB FAT32 file.
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This calculator is for educational purposes. Double-check important results before acting on them.