When to Use 20mhz vs 40mhz vs 80mhz

Improving and managing Wi-Fi performance is important to everyone, from home users to large enterprises. Channel width plays a big role in Wi-Fi performance. Selecting the right width can have a huge impact. Getting it right isn't always straightforward, though. With multiple standards and a variety of tradeoffs, it can be hard to keep up with best practices.

Every wireless environment is different, and you need to tailor your equipment to the conditions. With 2.4 GHz, increasing your channel width often isn't worth it, and you should stick with 20 MHz. Conversely, with 5 GHz, increasing channel width can improve performance, but there are tradeoffs. With 5 GHz, if you don't have to worry about interference and all your client devices support it, go with the highest width available.

For a practical example of how to optimize Wi-Fi, check out how CBT Nuggets trainer Keith Barker uses NetSpot and SweetSpots to examine channels for potential interference, map his coverage, and improve his home wireless network in this video:

Of course, there are plenty of "gotchas," and the rules of thumb above won't always be best for you. Like most things in tech, the right answer to this question depends on context. Let's explore the "why" behind these generalizations to help you gain a better understanding of the topic.

Understanding Wi-Fi Bands

Understanding Wi-Fi bands is vital to understanding when to use 20 MHz versus 40 MHz versus 80 MHz channel widths. It's also an important prerequisite to understanding Wi-Fi channels and channel width.

While 6GHz use cases are beginning to emerge (more on those later), the two main Wi-Fi bands are 2.4 GHz and 5 GHz. These Wi-Fi bands are then split into channels for wireless devices to communicate on.

2.4 GHz Wi-Fi Band

The 2.4 GHz band covers a 100 MHz range of 2400 MHz to 2500 MHz (equivalent to 2.4 GHz to 2.5 GHz). The 2.4 GHz band is split into 14 discrete channels that are 20 MHz each (more on other channel sizes in a bit).

Source: Wikimedia

Note in the image above that there are 14 channels in the 2.4 GHz band. Note that channels 1, 6, 11, and 14 do not overlap.

If you do the math, you'll quickly see that 14 bands of 20 MHz equals 180 MHz. This is greater than the 100 MHz size of the 2.4 GHz band, which means that channels overlap.

This is important to understand because overlapping Wi-Fi channels can interfere with one another. With 2.4 GHz Wi-Fi, there are four non-overlapping 20 MHz channels: 1, 6, 11, and 14. Note that due to varying regulations, not all channels are available for use in all locations. For example, only 11 channels are available in the United States.

5 GHz Wi-Fi Band

The 5 GHz Wi-Fi band covers a 150 MHz range from 5.725 GHz to 5.875 GHz. However, an additional range of Unlicensed National Information Infrastructure (UNII) bands widens that range to 750 MHz. Using 20 MHz, there are 24 non-overlapping channels available within the 5 GHz band. Note that this is a generalization, and available channels vary depending on location and channel size.

2.4 GHz vs 5 GHz: Popularity, interference, throughput, and range

2.4 GHz is more popular than 5 GHz at the moment, but both are widely used. 2.4 GHz is cheaper to implement than its 5 GHz counterpart, so manufacturers leverage it to save costs. 2.4 GHz has also been widely used for a longer period of time, so more 2.4 GHz devices have been deployed.

This popularity does have a downside, though. The prevalence of 2.4 GHz devices and limited number of non-overlapping channels with 2.4 GHz can exacerbate network congestion issues.

Many consumer devices, such as cordless phones and microwaves, use 2.4 GHz frequency bands. As a result, 2.4 GHz bands are more likely to experience interference. The relative abundance of non-overlapping channels on 5 GHz Wi-Fi makes it less susceptible to interference.

2.4 GHz vs 5 GHz: Which to Use?

In most cases, you should use 2.4 GHz to optimize for distance and 5 GHz to optimize for speed. However, there is a tradeoff between increased performance and range of coverage.

5 GHz is faster. 5 GHz Wi-Fi offers faster uploads and downloads than 2.4 GHz. Additionally, 5 GHz benefits from more non-overlapping channels and less interference, which can boost performance advantages. However, 5 GHz isn't as good at going through walls.

For instance, you should use 5 GHz for bandwidth-hungry use cases like online gaming (when a wired connection isn't possible) or high-definition video streaming. But keep your gaming console close to the router.

2.4 GHz goes further. The lower frequency of 2.4 GHz is better at passing through solid objects and can cover a wider range than 5 GHz. For comparison across different Wi-Fi 802.11 standards, here's a breakdown of different 2.4 GHz vs 5 GHz speeds and ranges.

For instance, you should use 2.4 GHz if your Wi-Fi clients and router/access point might be separated by multiple rooms. 2.4 GHz will do a better job of penetrating walls and objects between your Wi-Fi devices.

You can use both. It's also worth keeping in mind that simultaneous dual-band routers can broadcast 2.4 GHz and 5 GHz at the same time. This allows you to use 2.4 GHz for some devices and 5 GHz for others and can provide more flexibility. Additionally, if the 2.4 GHz and 5 GHz networks use the same SSID (service set identifier a.k.a. Wi-Fi network name), wireless devices can automatically connect to their preferred bandwidth. In short: simultaneous dual-band routers and modern smart devices can automatically do a lot of the work for you.

What about 6GHz WiFi?

In 2020, the United States Federal Communications Commission (FCC) authorized unlicensed use of the 6 GHz band. This change enables modern Wi-Fi standards to leverage 1.2 GHz of previously unavailable frequencies (5.925 GHz to 7.125 GHz). Largely Wi-Fi 6 was mostly developed before the availability of the additional bands, support for the 6 GHz band begins with Wi-Fi 6E. 

In addition to the performance boosts that can come with the additional bands, the new ranges that come with 6GHz are generally less congested than 2.4 and 5 GHz networks. 6 GHz Wi-Fi technology is not yet as common as 5 GHz, and device support is limited. However, we can expect adoption to ramp up in the years to come. 

It’s important to note that not all countries have fully adopted 6 GHz Wi-Fi. If you’re looking for support outside of the US, check out the Wi-Fi Alliance’s list of countries with regulations enabling 6 GHz Wi-Fi. 

What is Wi-Fi Channel Width?

When you're making a decision between 20 MHz vs 40 MHz vs 80 MHz vs 160 MHz what you're doing is picking a channel width.

We got an introduction to Wi-Fi channels above. We saw that the 2.4 GHz Wi-Fi band is chopped up into smaller 20 MHz bands for use. These smaller bands are the channels that Wi-Fi devices communicate on. The channel width is simply the frequency range for the channel.

20 MHz and 40 MHz: What's the Difference?

When dealing with Wi-Fi, channel widths are usually measured in megahertz (MHz). 20 MHz was the norm and only option for channel width in 802.11a and 802.11g Wi-Fi (more on the 802.11 standards below). The 802.11n standard introduced channel bonding, which enabled 40 MHz widths. 802.11ac further extended bonding to allow for 80 MHz and 160 MHz channels.

Bonding channels increase throughput, which can improve performance. Thus, the difference between 20 MHz and 40 MHz is throughput. 40 MHz has higher throughput than 20 MHz thanks to channel bonding.

There are downsides to channel bonding. While 40 Mhz might have higher throughput than 20 Mhz, it also reduces the number of non-overlapping channels. This increases the probability of interference. Additionally, not all Wi-Fi client devices support channels other than 20 MHz, so compatibility can be a concern.

A note on marketing lingo and tech talk: 20 MHz Wi-Fi channels are generally referred to as "narrow channels" or "narrow widths." 40, 80, and 160 MHz Wi-Fi channels are labeled "wide channels" or "wide widths."

Understanding IEEE 802.11 Standards

If you are exploring router specs, studying for a Network+, or trying to determine Wi-Fi compatibility, 802.11 has likely come up. IEEE develops the 802.11 Wi-Fi standards, and these standards dictate what speeds and frequencies are supported.

Here is a quick rundown on the well-known IEEE 802.11 standards:

• 802.11a was an early 5 GHz 54 Mbps Wi-Fi standard.

• 802.11b was a popular early 2.4 GHz 11 Mbps version of Wi-Fi.

• 802.11g increased 2.4 GHz Wi-Fi speeds up to 54 Mbps.

• 802.11n a.k.a. "Wi-Fi 4" supports both 2.4 GHz and 5 GHz Wi-Fi at speeds up to 450 Mbps.

• 802.11ac a.k.a. "Wi-Fi 5" supports 5 GHz only and speeds of up to 1300 Mbps.

• 802.11ax a.k.a. “Wi-Fi 6” and “Wi-Fi 6E” supports a theoretical max speed of 9.6 Gbps. Wi-Fi 6 supports 2.4 and 5 GHz bands. Wi-Fi 6E supports those two bands and adds support for the 6 GHz band. 

• 802.11be a.k.a. “WiFi 7” is expected to be ratified towards the end of 2024. Wi-Fi 7 theoretical max speeds will be around 46 Gbps, and it will support the 2.4, 5, and 6 GHz bands. 

Today, 802.11n, while still widely used, is beginning to show its age. 802.11ac is the norm for modern Wi-Fi technology, while 802.11ax popularity is rising.

It is important to note that maximum theoretical speeds are NOT the same as real-world speeds. In other words: With any given Wi-Fi version, you can expect slower actual speeds than the max speeds listed here.

What about Wi-Fi 7?

WiFi 7, based on the 802.11be IEEE standard, is still in a draft state. It is expected to be ratified towards the end of 2024. The Wi-Fi Alliance already has a Wi-Fi 7 certified program based on the draft standard, and there are “Wi-Fi 7” devices on the market. 

Wi-Fi 7 supports 2.4, 5, and 6 GHz bands and channel widths up to 320 MHz. The theoretical max speed of 46 Gbps is over four and a half times faster than Wi-Fi 6’s 9.6 Gbps. While most client devices won’t support Wi-Fi 7 for a while, expect this standard to be mainstream in the next 3-5 years. For a deeper dive into Wi-Fi 6E and Wi-Fi 7, check out The Future of Wi-Fi: What 6e and 7 Mean For You.

What's Dual-Band Wi-Fi?

Dual band refers to Wi-Fi routers that support both 2.4 GHz and 5 GHz bands. Using a dual-band router allows you to get the "best of both worlds." Higher speeds and lower interference for 5 GHz devices, and wider range for 2.4 GHz devices. It is very common for modern Wi-Fi routers to support dual-band functionality.

What’s Tri-Band Wi-Fi?

Tri-band Wi-Fi describes Wi-Fi technology that supports three Wi-Fi bands. Specifically, Wi-Fi devices that support the 2.4, 5, and 6 GHz bands are considered tri-band. Of the standards we’ve discussed in this article, only Wi-Fi 6E and Wi-Fi 7 are tri-band Wi-Fi. 

When to Use 20 MHz vs 40 MHz vs 80 MHz?

With an understanding of Wi-Fi frequencies and channel bonding, we can now dive into the decision-making process. As we go, remember that a prerequisite for using any particular channel width is device support.

2.4 Ghz WiFi: 20 MHz vs 40 MHz vs 80 MHz

If you're using 2.4 GHz, the answer is simple. The best bandwidth for 2.4 Ghz is 20 MHz.

In the majority of cases, using wide widths on 2.4 GHz isn't worthwhile.

The performance tradeoffs from interference on overlapping channels will likely outweigh the throughput benefits. One possible exception to this rule is remote areas where there are not many other Wi-Fi networks or devices.

Additionally, 2.4 GHz Wi-Fi and 20 MHz channel widths offer the broadest range of client device support. If you need to support legacy devices and Wi-Fi standards like 802.11b or 802.11g, you'll need 2.4 GHz and 20 MHz.

5 Ghz Wi-Fi: 20 MHz vs 40 MHz vs 80 MHz vs 160 MHz

With 5 GHZ, things get a bit less straightforward. There are valid use cases for multiple different Wi-Fi channel widths. The best bandwidth for 5 Ghz is 40 MHz. However, there are other considerations as well.

5 Ghz Wi-Fi: When to Use 20 MHz

If you have a 5 GHz router, consider using 20 MHz for maximizing the amount of non-overlapping channels. Regardless of using 2.4 GHz or 5 GHz, 20 MHz leaves you with the largest amount of non-overlapping channels. 20 MHz makes sense for high-density deployments and areas where interference is a major problem.

5 Ghz Wi-Fi: When to Use 40 MHz

Use 40 MHz to strike a balance between minimizing interference and maximizing throughput.

40 MHz offers more throughput than 20 MHz. It still leaves room for a dozen or so non-overlapping channels. This enables you to improve performance relative to 20 MHz and without risking the interference associated with 80 MHz.

5 Ghz Wi-Fi: When to Use 80 MHz

If Wi-Fi clients are close to your router, your Wi-Fi devices support 80 MHz, interference isn't a big issue, and you want to maximize throughput, consider 80 MHz.

If all your devices support it, and overlapping channels is not an issue, 80 MHz channels leave you with four or five non-overlapping channels. This increases the likelihood for interference. Additionally, clients often need to be very close (< 15 feet) to the Wi-Fi radio to get the most out of 80 MHz.

There are two common use cases for 80 MHz: mesh backhaul and bridging. However, any application where distances are minimal, and there isn't too much congestion can make sense for 80 MHz.

Conceptually, the takeaway here is that you must strike a balance between compatibility, throughput, and interference. While it seems intuitive that the right answer is always "up the width if you can," it just isn't that simple.

Interference from overlapping channels can wreak havoc on network speeds, so you must account for it. This is particularly important in cities, industrial areas, and large businesses where high levels of wireless traffic are common.

When to Use 160 MHz

With Wi-Fi 6 and later, 160 MHz can be useful in cases where there is low congestion and the devices in the network support 160 MHz bands. This is particularly true with the addition of the 6 GHz bands in Wi-Fi 6E that enable seven more 160 MHz channels to reduce overlap risk. 

How to Automate Wi-Fi Channel and Width Selection

As you can see, there's quite a bit to selecting Wi-FI channel and width selection. However, there are ways to automate the process.

For example, some Wi-Fi routers enable automatic detection and use of a channel size based on network conditions. This is usually achieved by selecting "Auto 20/40" or similar option as your channel width. Similarly, with most routers and devices, channel selection can be negotiated automatically. If you're not experiencing issues and aren't looking to optimize performance, sticking with these settings makes sense.

How Can I Check for Wi-Fi Interference?

If you are looking to optimize performance, a Wi-Fi network analyzer may help. Wireless network analyzers can help you identify interference on different channels and select the least noisy option. Alternatively, manually switching between channels and observing performance is a less scientific alternative.

Selecting the Right Wi-Fi Channel

When it comes to selecting the right Wi-Fi channel width, every situation is different. By understanding the fundamentals, you can more effectively select a configuration that works best for you. While there are no one-size-fits-all answers to the "20 MHz, 40 MHz, or 80 MHz?" question. However, understanding 2.4 GHz vs 5 GHz frequencies and the tradeoffs between non-overlapping channels and speed goes a long way.