Channel Width Calculator
Trade Wi-Fi channel width against PHY rate, noise-floor penalty and how many non-overlapping channels remain for reuse.
About Channel Width Calculator
Doubling the channel width doubles the subcarrier count and therefore the PHY rate, but it also doubles the received noise power, which costs 3 dB of link budget per doubling and halves the number of channels available for reuse. Wide channels are the single most over-used Wi-Fi setting: 80 MHz on a dense floor buys headline speed on one AP and co-channel interference on every other one.
Formula
Channel Width
PHY rate = data subcarriers × bits per subcarrier × coding rate × spatial streams ÷ 13.6 µs symbol time; noise penalty = 10·log10(width ÷ 20).
- subcarriers
- 802.11ax data subcarriers for the chosen width
- 13.6 µs
- 12.8 µs OFDM symbol plus a 0.8 µs guard interval
Worked example
With the default values below, Channel Width Calculator returns PHY Data Rate of 1,196. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Channel widthone of 20 MHz, 40 MHz, 80 MHz, 160 MHz, 320 MHz (Wi-Fi 7)
- 80 MHz
- Spatial streamsaccepts 1–8 streams
- 2 streams
- Bits per subcarrier (modulation)one of QPSK (2), 16-QAM (4), 64-QAM (6), 256-QAM (8), 1024-QAM (10), 4096-QAM (12)
- 1024-QAM (10)
- Coding rateaccepts 25–100 %
- 83 %
- MAC efficiency after overheadaccepts 20–95 %
- 65 %
Results
- PHY Data Rate
- 1,196 Mbps
- Expected TCP Throughput
- 778 Mbps
- Noise-Floor Penalty vs 20 MHz
- 6.0 dB
- Non-Overlapping Channels Available
- 6
- Data Subcarriers
- 980
Step by step
- 1Values used
- 2Channel Width
- 3PHY Data Rate= 1,196 Mbps
- 4Expected TCP Throughput= 778 Mbps
- 5Noise-Floor Penalty vs 20 MHz= 6.0 dB
- 6Non-Overlapping Channels Available= 6
- 7Data Subcarriers= 980
Assumptions and limits
- The result is derived only from the 5 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
How is Channel Width calculated?
PHY rate = data subcarriers × bits per subcarrier × coding rate × spatial streams ÷ 13.6 µs symbol time; noise penalty = 10·log10(width ÷ 20). Doubling the channel width doubles the subcarrier count and therefore the PHY rate, but it also doubles the received noise power, which costs 3 dB of link budget per doubling and halves the number of channels available for reuse.
Why does Channel Width matter?
Wide channels are the single most over-used Wi-Fi setting: 80 MHz on a dense floor buys headline speed on one AP and co-channel interference on every other one.
What values do I need to enter?
This calculator takes 5 inputs: Channel width, Spatial streams, Bits per subcarrier (modulation), Coding rate, MAC efficiency after overhead. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.