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Wi Fi Airtime Utilisation Calculator

Work out wi fi airtime utilisation instantly with clear inputs, formula shown and shareable results.

About Wi Fi Airtime Utilisation Calculator

Wi-Fi is a shared medium where the scarce resource is airtime, not bandwidth. A client transmitting at 24 Mbps takes eight times the airtime of one at 200 Mbps to move the same data, so a handful of distant clients can consume the channel. Utilisation above 80 percent means contention delay dominates and adding capacity is the only fix.

Formula

Airtime utilisation

demand = clients x per-client rate; airtime = demand / (data rate x 0.5 efficiency); slow-client case uses the lowest data rate

Worked example

With the default values below, Wi Fi Airtime Utilisation Calculator returns Airtime utilisation of 100.0%. Change any input above and every figure here is recalculated in your browser.

Inputs used

Active clientsminimum 1
25
Throughput each client needsminimum 0.001 Mbps
4 Mbps
Average client data rateminimum 0.1 Mbps
200 Mbps
Rate of the slowest clientsminimum 0.1 Mbps
24 Mbps

Results

Airtime utilisation
100.0%
Aggregate client demand
100.0 Mbps
Airtime if every client were slow
833.3%
Assessment
Airtime near saturation - add access points or reduce channel width

Step by step

  1. 1Values used
  2. 2Airtime utilisation
  3. 3Airtime utilisation= 100.0
  4. 4Aggregate client demand= 100.0 Mbps
  5. 5Airtime if every client were slow= 833.3
  6. 6Assessment= Airtime near saturation - add access points or reduce channel width

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 1 decimal place, 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 is the slow-client problem?

Also called the performance anomaly: because airtime is shared, one client at a low data rate consumes disproportionate airtime and drags down throughput for everyone on the radio.

How is it mitigated?

Airtime fairness scheduling, disabling the lowest data rates so distant clients must roam, and denser AP placement so clients are always near one.

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