Wireless networks (802.11) use three unlicensed frequency bands: 2.4 GHz, 5 GHz, and (since 2020) 6 GHz for WiFi 6E. Each band carves its spectrum into numbered channels — but the numbering systems, channel widths, and regulatory rules differ significantly between bands.
The 2.4 GHz band — crowded but universal
14 channels spaced 5 MHz apart from 2412 to 2484 MHz (channel 14 is an outlier at 2484 MHz, Japan-only and 802.11b only). The catch: each WiFi channel actually occupies 22 MHz at 20 MHz mode (or 40 MHz wide). With channels only 5 MHz apart, this means adjacent channels overlap heavily. The classic recommendation in the US/EU is to use channels 1, 6, 11 — the only non-overlapping 20 MHz options. This tool's overlap detector shows which channels conflict with your selection.
The 5 GHz band — more channels, but DFS
5 GHz splits into four sub-bands (the UNII bands):
- UNII-1 (5.15–5.25 GHz): channels 36, 40, 44, 48. Indoor + outdoor, no DFS.
- UNII-2A (5.25–5.35 GHz): channels 52–64. DFS required (Doppler weather radar).
- UNII-2C (5.47–5.725 GHz): channels 100–144. DFS required (military / aviation radar).
- UNII-3 (5.725–5.85 GHz): channels 149–165. No DFS, higher TX power allowed.
DFS (Dynamic Frequency Selection): APs must scan for radar pulses before transmitting on a DFS channel, and immediately vacate the channel if radar is detected during operation. This is why many consumer routers default to UNII-1 or UNII-3 — DFS adds complexity and brief connection interruptions.
The 6 GHz band — WiFi 6E & WiFi 7
5925–7125 MHz, opened for unlicensed WiFi in the US (FCC, April 2020) and many other regions since. Provides 59 channels at 20 MHz, or 29 at 40 MHz, 14 at 80 MHz, 7 at 160 MHz, and (WiFi 7) 3 at 320 MHz. The 6 GHz band has no DFS and far less congestion since it's brand-new — but requires WiFi 6E or WiFi 7 hardware on both client and AP. Lower TX power for "Low Power Indoor" mode; AFC (Automated Frequency Coordination) lets some outdoor / higher-power use.
Channel bandwidth tradeoffs
Wider channels (40, 80, 160, 320 MHz) carry more data per Hz of spectrum but consume more spectrum and reach less far. A 160 MHz channel at 5 GHz needs eight 20-MHz channels' worth of clean spectrum — often impossible in dense apartment-building environments. 80 MHz is the sweet spot for modern WiFi 6 in 5 GHz; 160 MHz is where WiFi 6E and 6 GHz shine because the band has so much more clean spectrum.
Why only channels 1, 6, and 11 in 2.4 GHz?
2.4 GHz channels are spaced 5 MHz apart but each WiFi signal occupies ~22 MHz (20 MHz channel + guard bands). So channels 1 and 2 overlap heavily, channels 1 and 3 overlap, etc. Only channels 1, 6, and 11 are far enough apart (5 channels × 5 MHz = 25 MHz separation) that they don't overlap. Using channels like 3, 8, 13 still works but creates interference with anyone on 1, 6, or 11 nearby. In EU/Japan you can also use channels 12 and 13; Japan has 14 (802.11b only). The US FCC limits to channels 1–11.
What is DFS and why does my WiFi disconnect on those channels?
DFS = Dynamic Frequency Selection. The 5 GHz channels 52–144 are shared with weather radar (UNII-2A, around 5.5–5.7 GHz) and military radar (UNII-2C). WiFi APs must monitor for radar pulses and immediately vacate the channel if any are detected — usually with a 30-minute "no return" period to that channel. Consumer routers often avoid DFS channels because the radar-scan startup delay (~60 sec) and runtime channel changes cause brief connection interruptions. Enterprise APs with proper certification handle this gracefully.
Should I use 80 MHz, 160 MHz, or 320 MHz channels?
It depends on your band and environment. 2.4 GHz: stick with 20 MHz — 40 MHz consumes the whole band and conflicts with neighbors. 5 GHz: 80 MHz is the sweet spot for most users. 160 MHz requires combining UNII-1 + UNII-2A (with DFS), or UNII-2C only, both of which can be tricky. 6 GHz: 160 MHz works well because there's so much clean spectrum, and 320 MHz (WiFi 7) is viable too. The wider the channel, the more bandwidth you get, but also the more vulnerable to any single source of interference. In congested apartments, narrower is often more reliable.
What's the difference between WiFi 6 and WiFi 6E?
WiFi 6 (802.11ax) operates on 2.4 GHz and 5 GHz, with new modulation (OFDMA), MU-MIMO improvements, and higher density support. WiFi 6E is the same protocol but extended to the new 6 GHz band (5925–7125 MHz). 6E requires hardware support on BOTH the AP and the client device — your 2020 phone won't see 6 GHz networks even if your router broadcasts on 6E. WiFi 7 (802.11be) goes further with 320 MHz channels (only available in 6 GHz), 4096-QAM, and Multi-Link Operation (MLO) for using multiple bands simultaneously.
Why is 5 GHz faster but shorter range than 2.4 GHz?
Physics. Lower frequencies (2.4 GHz) penetrate walls and obstacles better and diffract more around obstructions — but the 2.4 GHz band is narrow (~80 MHz total) so you can't fit wide channels. Higher frequencies (5 GHz, 6 GHz) attenuate faster through walls and have less diffraction, but the bands are much wider (~500 MHz in 5 GHz, 1200 MHz in 6 GHz), enabling much higher data rates via wider channels and more channels for less congestion. For range, 2.4 GHz wins. For speed in line-of-sight, 5/6 GHz wins.
Are channel 12 and 13 really unavailable in the US?
Mostly, yes. FCC Part 15 limits US 2.4 GHz WiFi to channels 1–11. Channels 12 and 13 are technically usable at reduced power (~50 mW EIRP vs 1000 mW for 1–11), but virtually no consumer router exposes them in US-region firmware, and clients typically refuse to associate on those channels in US mode. In EU, Japan, and most of Asia, channels 12 and 13 are full power. Channel 14 is Japan-only and limited to 802.11b (the original CCK modulation, no OFDM).