Which Zigbee Channel Fits Around Your Wi-Fi?

How to use it

1. Open a Wi-Fi scanner on a phone or laptop and note every 2.4 GHz network it lists, your own router included. Add one row per network with its channel and width.
2. If a network runs 40 MHz, say so. It occupies twice the spectrum of a 20 MHz one. If you don't know which half it uses, leave it on "Not sure" and the planner assumes the worst case.
3. Enter how many Zigbee devices are mains-powered and how many run on batteries. The mesh check under the inputs reacts straight away.
4. Pick your current Zigbee channel, or leave it on "Not set up yet" if you're still planning. A network that doesn't exist yet is the cheapest one to configure.
5. Read the recommendation, then the warnings, then the table. The diagram is there so you can see the overlap instead of taking a score on trust.

Where the channel table comes from

The planner doesn't guess at frequencies. Zigbee runs on IEEE 802.15.4, and the 2.4 GHz part of that standard numbers its channels 11 to 26, each centred on 2405 + 5 x (k - 11) MHz, which puts them 5 MHz apart. The standard text itself (IEEE Std 802.15.4-2003, clause 6.1.2) states that formula and says sixteen channels exist in this band. NXP's coexistence application note (JN-AN-1079) tabulates the same plan in its appendix C and gives each channel a width of about 2 MHz.

Wi-Fi in 2.4 GHz numbers its channels 1 to 13 (14 is a special case the planner leaves out), with the centre at 2407 + 5 x n MHz. MathWorks' documentation on WLAN radio frequency channels gives the 2.407 GHz starting point and the 5 MHz step, NXP's appendix D lists the thirteen centres from 2412 to 2472 MHz, and Annex E of the 802.15.4 standard draws channels 1, 6 and 11 at 2412, 2437 and 2462 MHz. A legacy 802.11b channel is 22 MHz wide. Newer 802.11g and 802.11n transmissions use 20 MHz, and the 2.4 GHz band allows bonding two of them into 40 MHz, as the list of WLAN channels describes. The planner offers all three widths.

These tables are generated by the same functions the planner uses, so the page and the maths can't disagree. Wi-Fi spans assume the 20 MHz width of 802.11g and 802.11n. A legacy 802.11b channel is 22 MHz wide, which adds 1 MHz on each side.

Check the rules where you live

Which of these channels you may use differs between regions. Both the Wi-Fi and the Zigbee channel lists are shorter in some places than the standards define, and the 802.15.4 standard itself says a compliant device supports the channels its region allows. The planner shows everything the standards define and picks no side. Look up the radio rules for your region first, and treat any channel you can't use as crossed off.

What the score does and doesn't mean

Here's the whole method. For every Zigbee channel the planner asks one question per Wi-Fi network: does this 2 MHz sit inside the network's band? Inside costs 100 points. Outside but near the edge costs a little, because a Wi-Fi transmission doesn't stop cleanly at its nominal edge. The 802.15.4 standard's own coexistence annex assumes an 802.11b transmitter is only 30 dB down between 11 and 22 MHz from its centre, not silent. The Zigbee and Wi-Fi coexistence guide that MetaGeek published makes the same point about sideband lobes catching Zigbee channels 25 and 26 next to a Wi-Fi network on channel 11.

Then there's a second kind of penalty that has nothing to do with spectrum. The Home Assistant ZHA documentation recommends channels 15, 20 and 25 to avoid interoperability problems, and the Zigbee2MQTT documentation recommends 11, 15, 20 and 25, the channels used by Zigbee Light Link. Channel 26 is often the emptiest and still isn't on either list, so it takes a flat penalty. Is that fair? It's a judgement, which is why the table shows the Wi-Fi impact and the penalty side by side. If you know every device you own works on 26, you can read past it.

What it can't know is how busy each network is. A neighbour's router idling and one streaming video all evening look identical to the planner, because both are just a band on the page. The result is a plan for a layout, not a forecast of your air.

Changing the channel is the expensive part

Choosing a channel before the network exists costs nothing. That's the case the planner treats as the default. Moving a live network is where the price shows up. Zigbee2MQTT's documentation says that devices asleep during the channel broadcast, usually battery ones, only switch when they next wake, that some devices don't support a change at all, and that channel changes work with some adapter families and not others. The ZHA documentation adds that reconnecting can take up to an hour and that the best practice is not to change the channel from the default without a reason. It also says that trying a fixed Wi-Fi channel first is usually the cheaper move. The checklist the planner prints is built from exactly those statements, with your battery count filled in.

Routers decide whether the mesh exists

The second box under your inputs checks something unrelated to spectrum. In Zigbee, mains-powered devices such as bulbs and plugs normally act as routers and relay for everyone else, while battery devices are end devices that don't relay. The ZHA documentation notes that the zigpy library it builds on has an upper limit of 32 direct children, and that router devices are how a network grows past that. Zigbee2MQTT adds a caveat worth knowing: most mains-powered relays that need no neutral wire don't route. So count the devices that actually relay, and keep them powered. The ratio the planner warns about, more than eight battery devices per router, is its own rule of thumb and not a specification, which the warning says out loud.

Where this planner comes from

I built it while planning the Zigbee layer of a house that isn't running on Zigbee yet. I haven't bought the lighting controllers, so nothing on this page is a result from that house. There is no channel collision on record there, and no pairing it rescued. On paper the plan is a few dozen devices, mostly mains-powered bulbs and switches, which is exactly the situation the router check and the channel-first approach exist for. That's all the page claims.

Want the surrounding decisions? The guide to Zigbee coordinators for Home Assistant covers the adapter you'll plug into, and the Zigbee2MQTT setup guide shows where the channel setting lives once you've picked a number.