A WiFi channel is a small segment of a frequency through which our wireless networks can send and receive data.
Basically , each frequency bands ( 2.4Ghz or 5Ghz) has a specific allowed range to be use in WiFi networks. For technical reasons, the standard organizations have divided these range to channels (14 channels in 2.4Ghz and 25channels in 5Ghz frequency bands) , each with specific broad, which is known as Channel Width.
In 2.4Ghz band , each channel has 20Mhz width , but in 5Ghz , each channel can have 20,40,80 or 160Mhz width. The width of WiFi channel determines how much data can pass through the channel in a period of time.
Suppose the channel as a highway and the channel width as highway’s width. The wider the highway, the more traffic (data) can pass through. By increasing the channel width, we can increase the speed and throughput of WiFi network. ( Read More : WiFi Standards Chart )
In theory, the wider channel provides more bandwidth, but you should consider the effect of interferences and devices compatibility. Now that you know the channel and channel width concepts, we can make a right decision for channel width selection.
Use 20Mhz channel width in 2.4Ghz band, in such cases :
With 20Mhz channel-Width in 2.4Ghz band, you will have 3 non-Overlapping channels(1,6,11).
Use 20Mhz channel width in 5Ghz band, in such cases :
With 20Mhz channel-Width in 5ghz band , you will have 8 non-Overlapping channels(36,40,44,48,149,153,157,161).
The 40Mhz channel Width is created by Bonding two 20Mhz channels, commonly used in 5ghz band. The 40Mhz channel Width enables you to improve performance compared to 20Mhz channel width.
But consider in mind, the wider the channel, the higher the probability of the negative effect of the interferences. Before setting your router to 40Mhz Channel Width , check the interference level by WiFi-Analyzer tools to find the least-crowded channel.
With 40Mhz channel-Width in 5ghz band , you will have 4 non-Overlapping channels(38,46,151,159).
The 80Mhz channel Width is supported by WiFi5 (802.11ac) and WiFi6 (802.11ax) devices, with only 2 non-overlapping channels. So, increases the possibility of interference. Consider in mind, due to technical reasons, the clients should be close to the router to take advantage of 80Mhz channel width. Typically , the 80Mhz is using for Mesh-backhaul and bridging between routers.
With 80Mhz Channel-Width, you will have 2 non-Overlapping channels(42,155).
The real 160Mhz channel-width is introduced in 802.11ac (WiFi5) and optimized in 802.11ax (WiFi6) technology, with only 1 non-overlapping channel. We should wait for the technical grow in both routers and clients to be able to use that. Read More : WiFi6 Technical Specifications.