Bitrate Calculator
Calculate combined audio/video bitrates, fit targets to file sizes, and verify streaming requirements.
Video Settings
Audio Settings
How Video Bitrate & File Size Are Calculated
Raw (uncompressed) video bitrate is computed as Width × Height × Frame Rate (FPS) × Bit Depth × Color Channel Factor (usually 3). Modern compression standards shrink this stream significantly: AVC/H.264 compresses by roughly 20:1, HEVC/H.265 by 40:1, and newer codecs like AV1 by up to 50:1.
File size is the integration of total combined bitrate (Video Bitrate + Audio Bitrate) over time: File Size = (Combined Bitrate in bps / 8) × Duration in seconds. Using the bidirectional "Fit to Size" equation, you can invert this relationship: Allowable Bitrate = Target File Size in bits / Duration. This tool lets you estimate streaming ingestion caps, fits videos to target files, and plans network requirements client-side.
Built and maintained by Meet Shah · Last updated
What this tool is used for
- Estimating a video file's size from its bitrate and duration.
- Working out the bitrate a target file size allows.
- Comparing two codecs at the same visual quality target.
- Sizing a stream against an upload bandwidth.
- Checking an encoder's setting against the resulting file.
Frequently Asked Questions
- How does bitrate relate to file size?
- Size = bitrate × duration, then divided by 8 to get bytes. A 10 Mbps video running 10 minutes is 10 × 600 ÷ 8 = 750 MB. The audio track adds its own bitrate on top, which is the term most often left out of a quick estimate.
- What is the difference between CBR and VBR?
- Constant bitrate spends the same data on every second regardless of content; variable bitrate spends more on complex scenes and less on simple ones. VBR gives better quality per byte, CBR gives predictable size and smoother streaming — which is why live streams use it.
- Why does the same bitrate look different across codecs?
- Because compression efficiency differs substantially. H.265 and AV1 achieve roughly the same quality as H.264 at around half the bitrate, so a figure that is generous for AV1 is inadequate for H.264. Bitrate targets are only meaningful alongside the codec.
- What bitrate does streaming need?
- Broadly 5 Mbps for 1080p30, 8 for 1080p60, and 15–25 for 4K on H.264 — with platform guidance varying. Uploading above the platform's ceiling is wasted, since it re-encodes everything to its own ladder regardless of what you sent.
- Is audio bitrate measured the same way?
- Yes, and the numbers are far smaller. 128 kbps MP3 is the old "good enough" mark and 256 kbps AAC is transparent for most listeners. Lossless is roughly 1,400 kbps for CD audio, which is why the difference in file size is an order of magnitude.
Common errors and gotchas
- Confusing bits with bytes, which is a factor of eight and the usual source of a wrong file size.
- Forgetting the audio track, which adds to the total bitrate.
- Using an average bitrate for a variable-bitrate encode, where peaks matter for streaming.
- Comparing bitrates across codecs, where a newer codec looks better at the same number.
- Ignoring container overhead, which is small but not zero.