Free tool by DCAST
Bitrate & File Size Calculator
File size from bitrate and duration, or required bitrate from target size. Resolution, FPS, and audio tracks. For streaming and VOD.
Inputs
Presets fill resolution and bitrate; adjust as needed.
Video & time
Bitrate
Total bitrate = video + (audio × tracks).
Optional: live stream upload check
Use 70–80% of upload speed for stable streaming.
Result
Estimated file size: 2.31 GB
Total bitrate: 5.13 Mbps (video + audio × tracks)
Pixels per second: 62.21 Mpx/s (reference)
Formula: Size (bytes) = (Video + Audio × Tracks) × Duration(sec) × 10⁶ ÷ 8. For same quality, HEVC/AV1 need lower bitrate than H.264 — see Duration calculator and Codec cheat sheet.
How the bitrate calculator works
This calculator estimates video file size from bitrate and duration, or the bitrate you need to fit a target file size. Total bitrate is the sum of video bitrate and all audio tracks (audio bitrate × number of tracks). For live streaming, keep total bitrate below about 75% of your upload speed to avoid buffering.
Resolution and frame rate do not change the file size directly; they affect the recommended bitrate for a given quality. For the same bitrate, HEVC and AV1 produce smaller files than H.264 at similar quality. See the duration calculator for encoding time and the codec cheat sheet for codec comparison.
- Q:What is video bitrate?
- A:Bitrate is the number of bits per second used to encode video (and audio). Higher bitrate usually means better quality and larger file size. It is measured in Mbps (megabits per second) or kbps (kilobits per second).
- Q:How is file size calculated from bitrate?
- A:File size (bytes) = (video bitrate + audio bitrate × number of audio tracks) × duration in seconds × 1,000,000 ÷ 8. The calculator uses this formula for both "file size from bitrate" and "required bitrate from target size" modes.
- Q:What bitrate should I use for streaming?
- A:Use 70–80% of your upload speed for stable live streaming. Twitch recommends up to 6,000 kbps for 1080p60; YouTube allows higher. Choose a preset (Twitch, YouTube, 4K) or enter your own values.
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