Bitrate Calculator

What this calculator works out

Encoding and contribution links are usually planned in two numbers: how much bandwidth the streams need end to end, and how much disk the recordings will fill. This calculator produces both from a single bitrate figure, so you can size a link or a storage volume before committing to an encoder profile.

• Total throughput — the aggregate bandwidth of every input and output at the chosen bitrate.
• File size, single output — what one output records over the given duration.
• File size, all outputs — the same figure multiplied across every output and stream.

How the numbers are calculated

Throughput is the bitrate multiplied by the combined count of inputs and outputs, multiplied again by the number of streams — inputs are counted because a contribution link carries the ingest as well as the distribution copies. File size divides the bitrate by eight to convert bits to bytes and multiplies by the duration in seconds.

Bitrates use decimal units, so 1 Mbps is 1,000 kbps. File sizes use binary units, so 1 MB is 1,024 KB — the convention most encoders and file managers report in. Results are rounded to two decimal places, and the output units can be changed after calculating without re-entering anything.

Worked example

A 27 Mbps mezzanine feed with one input, one output and one stream needs 54 Mbps of throughput, and 30 seconds of it records to roughly 98.9 MB.

Things it deliberately ignores

The figures are payload only. Container overhead, MPEG-TS null packets, IP and UDP headers, and FEC or SRT retransmission traffic all sit on top — allow headroom over the throughput number rather than provisioning a link at exactly the figure shown.