Zigbee and Thread channel planner
Wi-Fi, Zigbee, Thread, Bluetooth and your microwave all share 2.4 GHz. This works out where the quiet space is in your particular house.
The arithmetic behind the answer#
There is no mystery here, just two formulas and some subtraction.
- 802.15.4 channel center frequency = 2405 + 5 x (channel number - 11) MHz, for channels 11 through 26. Each channel occupies roughly 2 MHz at the 3 dB points and around 3 MHz out to the first nulls.
- Wi-Fi 2.4 GHz channel center frequency = 2407 + 5n MHz. So channel 1 is 2412 MHz, channel 6 is 2437 MHz, channel 11 is 2462 MHz.
- A 20 MHz Wi-Fi channel occupies its center plus and minus 10 MHz. Legacy 802.11b occupies plus and minus 11 MHz, and spectral mask sidelobes leak further still.
Run those numbers and the picture is unambiguous: Wi-Fi channel 1 covers 802.15.4 channels 11 to 14, Wi-Fi 6 covers 16 to 19, and Wi-Fi 11 covers 21 to 24. The complete table is on the interference page, along with the two caveats that stop this being a simple "always use 26" rule.
Before you change anything#
Three things to check first, because they cause more trouble than channel choice does:
- Is your coordinator plugged into a USB 3.0 port or sitting next to an SSD? USB 3.0 emits broadband noise across 2.4 to 2.5 GHz, about 20 dB of it at close range. It is in-band, so it cannot be filtered. A one to two meter USB 2.0 extension cable fixes it, and this is the single most common cause of a "bad" Zigbee network.
- Do you have enough mains-powered routers? Both Zigbee and Thread rely on always-on devices to relay. A network of nothing but battery sensors has no mesh, only a lot of hopeful shouting. See Thread mesh design.
- Is your Wi-Fi actually on 1, 6 or 11? Many routers auto-select and land on channel 3 or 9, which overlaps two of the three clean spots at once. Pinning Wi-Fi to 1, 6 or 11 is usually more valuable than moving Zigbee.
What is the best Zigbee channel?
Channel 25 or 26 in most US homes, because those are the only ones clear of Wi-Fi channels 1, 6 and 11. Channel 26 has the best separation but two real drawbacks: many radios reduce transmit power on it in North America to stay clear of the FCC restricted band edge at 2483.5 MHz, and plenty of older or budget Zigbee devices refuse to join it at all.
Can Zigbee and Thread share a channel?
They can, and they should not. They use the same physical layer, so two networks on the same channel compete for the same airtime with no coordination between them. Put them at least three channels apart, and keep both away from your Wi-Fi.
Will changing the channel fix my dropouts?
Only if interference is actually the cause. Dropouts concentrated in one room are usually a coverage problem, not a channel problem. Dropouts that started when you got a new router, or that follow the microwave running, point at interference. The device unresponsive guide works through the causes in order.
Does 5 GHz Wi-Fi help?
Indirectly, and it is worth doing. Almost all smart home devices are 2.4 GHz only, so you cannot move them, but you can move everything else. Pushing phones, laptops and TVs onto 5 or 6 GHz frees 2.4 GHz airtime for the devices that have no choice. See the network a smart home wants.