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Conversion

Video Bitrate ↔ File Size Calculator

Solves both directions: (1) forward — enter duration, video and audio bitrate, get the final file size (GB / MB / GiB / MiB); (2) inverse — enter a target file size and duration, back out the required video bitrate. Use for YouTube upload sizing, Twitch / OBS live-stream bitrate, SD-card / SSD capacity planning and editing-ingest budgeting.

Resulting file size

4.59 GB

4.27 GiB

MB

4 586

MiB

4 374

Total bitrate

10.19 Mbps

bits / sec

10 192 000

Formula: file = (video Mbps × 1 000 000 + audio kbps × 1 000) × duration ÷ 8. MB is decimal 10⁶ bytes; MiB is binary 2²⁰ bytes (Finder and Windows Explorer typically display MiB / GiB).

Formula

file_bytes = (video_Mbps × 1 000 000 + audio_kbps × 1 000) × duration_sec ÷ 8. Inverse: required_video_Mbps = [target_MB × 8 ÷ duration_sec − audio_kbps] ÷ 1 000.

Frequently asked

What's the difference between Mbps, MB/s and MiB/s — I keep mixing them up.

Lower-case "b" = bit; upper-case "B" = Byte = 8 bits. So 1 Byte = 8 bits and 1 MB/s = 8 Mbps. Example: 100 Mbps broadband ÷ 8 = 12.5 MB/s actual download speed. The M vs Mi prefix is decimal (10⁶) vs binary (2²⁰ = 1 048 576): 1 MB = 1 000 000 bytes; 1 MiB = 1 048 576 bytes — about 4.86 % apart. Networking / CDN / streaming traditionally use decimal; disk / RAM / OS file managers traditionally use binary. This tool reports both so you can match whichever number you're comparing against.

What bitrate should I pick for a 1-hour 4K 60fps clip?

YouTube's 4K 60fps H.264 guideline is 53 – 68 Mbps, +25 % for HDR. Pick 60 Mbps + 192 kbps AAC: one hour → (60 × 10⁶ + 192 × 10³) × 3 600 ÷ 8 ≈ 27.1 GB. If you re-encode in HEVC (H.265) or AV1 you can cut bitrate roughly in half (28 – 35 Mbps) for similar visual quality, dropping the file to ~ 13 GB — at the cost of much slower encoding. For pure local archival of edit-grade footage, ProRes 422 or DNxHR are common: visually transparent but enormous (ProRes 422 4K 60fps ≈ 471 Mbps → ~ 200 GB / hour). This tool lets you sweep through bitrates to balance quality, file size and upload time before committing.

What does the "audio overrun" message in the inverse mode mean?

Your target file size is so small that the audio bitrate × duration alone would exceed it, leaving no budget for video — the formula returns a negative video bitrate. Example: target 1 MB, 5 min duration, audio 128 kbps → audio alone needs 128 × 1000 × 300 ÷ 8 = 4.8 MB, larger than the 1 MB target. Fixes: (a) lower the audio bitrate (talking-head / podcast often runs fine at 64 kbps, mono 32 kbps, or Opus 16 kbps in extremis); (b) increase the target file size; (c) drop the audio entirely (set audio = 0).

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