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.
Enter non-negative values; the inverse mode also requires a positive duration and target size.
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
Required video bitrate
2.04 Mbps
2 044 kbps
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.
- · Uses decimal units (MB = 10⁶ bytes, GB = 10⁹ bytes) — what macOS Finder, AWS S3 and CDN billing report.
- · Also shows binary units (MiB = 2²⁰ bytes, GiB = 2³⁰ bytes) — what Windows Explorer, Linux `du` and SD-card labels report.
- · YouTube recommended SDR 30 fps H.264 bitrates: 1080p ≈ 8 Mbps; 1440p 16; 4K 35 – 45; 8K 80 – 160. HDR adds ~ 25 %.
- · Twitch caps 1080p60 at 6 Mbps (8 Mbps for Partners); YouTube Live recommends 4.5 – 9 Mbps for 1080p60; TikTok Live ≈ 4 Mbps.
- · Common audio bitrates: YouTube AAC 192 kbps; Spotify high-quality 320 kbps; Twitch 160 kbps; Discord 96 kbps; silent video = 0.
- · Bitrate inputs are *averages*. VBR (variable bitrate) actual files run ± 5 – 15 % vs the formula; CBR (constant bitrate) matches exactly.
- · The inverse mode returns an error when the audio alone exceeds the target file size (would require negative video bitrate). Lower the audio kbps or raise the target MB.
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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