Find non-overlapping WiFi channels and center frequencies for 2.4GHz and 5GHz bands.
In the 2.4 GHz band, each 20 MHz-wide channel is spaced only 5 MHz apart in center frequency, so adjacent channels overlap significantly; only channels 1, 6, and 11 are spaced far enough apart (20 MHz or more) to avoid overlapping entirely, which is why they are the standard recommendation. The 5 GHz band has far more spectrum divided into channels that are inherently non-overlapping at 20 MHz width, giving many more usable channels — though some (52-144) are subject to Dynamic Frequency Selection (DFS) rules to avoid interfering with radar systems.
2.4GHz channel overlap condition
Channels overlap if |channel_A − channel_B| × 5 MHz < 20 MHz (i.e. separated by fewer than 4 channel numbers)
Each 2.4GHz channel is 20 MHz wide but channels are numbered only 5 MHz apart, so adjacent channel numbers overlap heavily. Channels 1, 6, and 11 are the only three spaced at least 20 MHz apart from each other, making them the only fully non-overlapping combination.
The 5GHz band has much more total spectrum allocated to WiFi, and it's divided into 20 MHz segments that don't overlap by design, unlike 2.4GHz's tightly packed channel numbering — giving 20+ independent channels instead of just 3.
Dynamic Frequency Selection (DFS) channels (roughly 52-144) share spectrum with weather and military radar. Devices using these channels must detect radar signals and vacate the channel within seconds if radar is present, which can occasionally cause brief disconnects.
It increases interference risk with neighboring networks on overlapping channels, degrading throughput for both networks, but won't necessarily prevent connectivity — the practical impact depends on how many other networks are nearby and how congested the band already is.