Skip to content
ENExplore Calculators

Token Bucket Size Calculator

Work out token bucket size instantly with clear inputs, formula shown and shareable results.

About Token Bucket Size Calculator

A token bucket refills at the committed rate and its depth determines how long traffic may exceed that rate. Two constraints apply: the bucket must hold the burst you want to permit, and it must hold at least one round trip of data — 1.5 round trips is a safer rule — so TCP's window growth is not mistaken for a violation.

Formula

Bucket sizing

burst bytes = rate x burst duration / 8; RTT bytes = rate x RTT / 8; recommended = max(2 x MTU, burst bytes, 1.5 x RTT bytes)

Worked example

With the default values below, Token Bucket Size Calculator returns Recommended bucket size of 732.42 KiB. Change any input above and every figure here is recalculated in your browser.

Inputs used

Token fill rateminimum 0.001 Mbps
100 Mbps
Burst duration to allowminimum 0.1 ms
50 ms
MTUaccepts 64–9,216 bytes
1,500 bytes
Typical round-trip timeminimum 0.1 ms
40 ms

Results

Recommended bucket size
732.42 KiB
Size from the burst window
610.35 KiB
Size from one round trip of data
488.28 KiB
Burst the recommended bucket allows
60.00 ms

Step by step

  1. 1Values used
  2. 2Bucket sizing
  3. 3Recommended bucket size= 750,000
  4. 4Size from the burst window= 625,000
  5. 5Size from one round trip of data= 500,000
  6. 6Burst the recommended bucket allows= 60.00 ms

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

What happens if the bucket is too small?

Normal TCP bursts are dropped, throughput collapses well below the committed rate, and the symptom looks like a slow link rather than a misconfigured policer.

Can the bucket be too large?

Yes. A very deep bucket lets long bursts through at line rate, which defeats the purpose of rate limiting and can overwhelm downstream buffers.

Related Calculators

Token Bucket Size Calculator | Calcrivo