WiFi Channel Overlap Calculator

2.4 GHz has 14 numbered channels, but each one is only 5 MHz apart on the dial and a single channel occupies 22 MHz of spectrum (the 802.11 DSSS/OFDM mask in this band). To keep two channels from stepping on each other you need at least 25 MHz of separation, which is exactly the gap from 1 to 6 and from 6 to 11. Any other set (1, 5, 9 or 2, 7, 12) leaves channels close enough that their masks overlap, and an AP set to a channel between 1, 6, and 11 ends up interfering with two of the three clean slots at once. That is why every consumer router still defaults to one of those three numbers.

The FCC carved 5 GHz into four sub-bands. UNII-1 covers channels 36-48 and is low-power indoor with no DFS, so it is the easiest band to deploy. UNII-2A (52-64) and UNII-2C (100-144) are DFS bands shared with weather and military radar; APs there must listen for radar and vacate the channel if they hear it. UNII-3 (149-165) is full-power, no DFS, and is the other crowd-favorite alongside UNII-1. Together they give you up to 25 distinct 20 MHz channels, which is why 5 GHz is so much easier to plan than 2.4 GHz.

DFS stands for Dynamic Frequency Selection. On 5 GHz channels 52 through 144 the AP shares spectrum with weather and military radar, and the rules require the AP to listen for at least 60 seconds before transmitting on a DFS channel for the first time (the channel availability check). If radar is detected later, the AP has to stop transmitting on that channel within 10 seconds and pick a new one. In practice that means a brief outage and a possible drop to a non-DFS channel like 36 or 149, which is why our recommender prefers a non-DFS clean channel when one is available.

Wi-Fi 6E (802.11ax in the 6 GHz band) added 1200 MHz of fresh spectrum, with up to 59 non-overlapping 20 MHz channels, 29 at 40 MHz, 14 at 80 MHz, 7 at 160 MHz. Critically, there are no legacy 802.11b/g/n clients there, so airtime is not consumed by slow management frames, and there is no radar to share with, so no DFS. The catch is range: 6 GHz attenuates faster than 5 GHz, so you typically need more APs at slightly lower power, and only Wi-Fi 6E or Wi-Fi 7 client devices can see the band at all.

320 MHz channels are a Wi-Fi 7 (802.11be) feature and only exist in the 6 GHz band, which gives the spectrum room to fit them. You need both a Wi-Fi 7 AP and a Wi-Fi 7 client (Snapdragon X80 / X75 phones, recent Intel BE200/BE201 laptops, the latest Apple silicon Macs) to negotiate one. The throughput payoff is real, roughly double a 160 MHz channel, but the trade-off is the same as 160 MHz: a wider channel means more aggregate interference from neighbors, and in a dense apartment building 80 MHz often beats 320 MHz on real-world throughput.