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Concurrent Call Capacity Calculator

Work out concurrent call capacity instantly with clear inputs, formula shown and shareable results.

About Concurrent Call Capacity Calculator

Call capacity is the voice reservation divided by per-call bandwidth. The reservation matters because voice needs a priority queue with a guaranteed share, and Cisco's long-standing guidance is to keep that below about a third of the link so best-effort traffic is not starved. Signalling and RTCP take a further small slice.

Formula

Call capacity

voice bandwidth = link x reservation x (1 - signalling overhead); calls = floor(voice bandwidth / per-call bandwidth)

Worked example

With the default values below, Concurrent Call Capacity Calculator returns Concurrent calls supported of 330. Change any input above and every figure here is recalculated in your browser.

Inputs used

Available link bandwidthminimum 0.001 Mbps
100 Mbps
Bandwidth per callminimum 1 kbps
95 kbps
Share reserved for voiceaccepts 1–100 %
33 %
Signalling overheadaccepts 0–50 %
5 %

Results

Concurrent calls supported
330
Bandwidth allocated to voice
31,350 kbps
Bandwidth consumed per call
95.0 kbps
Bandwidth left for data
67.00 Mbps

Step by step

  1. 1Values used
  2. 2Call capacity
  3. 3Concurrent calls supported= 330
  4. 4Bandwidth allocated to voice= 31,350 kbps
  5. 5Bandwidth consumed per call= 95.0 kbps
  6. 6Bandwidth left for data= 67.00 Mbps

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, 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

Why cap the priority queue at a third of the link?

Beyond that, data traffic experiences severe starvation during voice peaks. It is a practical rule rather than a hard limit, but exceeding it needs careful testing.

Does call admission control matter?

Critically. Without it, the call beyond capacity is accepted and degrades every existing call rather than being rejected cleanly.

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