Convert between duration, file size and bitrate for audio and video — in your browser.
Bitrate is the amount of data a piece of audio or video consumes per second, and it ties together the three quantities every media workflow cares about through one simple relation: file size equals bitrate multiplied by duration. This calculator solves that relation in all three directions. Give it duration and size to find the average bitrate of an existing file; give it duration and bitrate to predict how large a recording or export will be; give it size and bitrate to work out how long a recording can run before it fills the available space.
Internally, everything is converted to bits and seconds before dividing, using the decimal convention the media world actually uses: 1 MB = 8,000,000 bits, 1 GB = 8,000,000,000 bits, 1 Mbps = 1,000 kbps. That matches how encoders such as FFmpeg and platforms such as YouTube report rates. The classic trap in these calculations is mixing bits with bytes — network rates are measured in bits per second, file sizes in bytes, and the factor of 8 between them explains most "impossible" results. The tool shows the full calculation next to every answer so you can see exactly which conversion was applied.
Typical uses: checking whether an exported video fits an upload or e-mail limit, dimensioning storage for security-camera footage or podcast archives, estimating how much mobile data a stream will burn, or sanity-checking encoder settings against the reference presets shown under each result (MP3 at 128–320 kbps, 1080p video around 8 Mbps, 4K around 45 Mbps). All calculations run 100% in your browser as you type — nothing is uploaded and no server is involved.
Bitrate = size in bits ÷ duration in seconds · Size = bitrate × duration · Duration = size ÷ bitrate. Decimal units: 1 MB = 8,000,000 bits · 1 GB = 8,000,000,000 bits · 1 Mbps = 1,000 kbps.
Bitrate is the amount of data used per second of media, measured in bits per second — usually kbps for audio and Mbps for video. For the same codec, a higher bitrate generally means better quality and a proportionally larger file.
Because the calculation covers only the audio/video stream itself. Real files add container overhead (MP4, MKV) plus extra tracks such as subtitles, typically a few percent. With variable bitrate (VBR) encoding, the actual average rate also fluctuates around the target.
Mbps measures megabits per second and MB/s measures megabytes per second: 1 byte = 8 bits, so 8 Mbps = 1 MB/s. Internet speeds are quoted in bits, file sizes in bytes — this factor of 8 is the most common source of confusion in bitrate math.
Common references: 128–320 kbps for MP3 audio, 96–160 kbps for streaming AAC, about 8 Mbps for 1080p video and about 45 Mbps for 4K, in line with YouTube upload recommendations. Fast motion and fine detail push the useful bitrate up.
No. All calculations run 100% in JavaScript on your device — nothing is uploaded, transmitted or stored on any server.
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