If you're having problems with Wi-Fi, such as slow internet or dropped connections, or you simply want to find out if there's a strong enough signal at your front door to install a smart doorbell, we'll explain how to do it.
Knowing the strength of the Wi-Fi signal in various places around your home will also help you to know whether it's worth replacing your router with a mesh Wi-Fi system, where you can locate security cameras outdoors, as well as diagnosing any problems particular devices might be having.
All you need to check signal strength is an iPhone or Android phone and a free app.
What's a good Wi-Fi signal strength?
Before we get into the apps and testing, it’s important to know what the numbers mean, otherwise they'll be meaningless.
Signal strength is expressed as a percentage or, more commonly, an RSSI value in dBm. RSSI simply stands for received signal strength indicator, and this is what the apps below will show you.
The closer the value is to 0, the stronger the signal is. That sounds backwards, but it's because the values are negative. So, a higher number means a worse signal, a lower number a stronger one.
It’s not a linear scale, either. A drop of 3dBm (say from -50 to -53dBm) means the signal is half as strong. Conversely, an increase of 3dBm means the signal is twice as strong.
Here’s a general guide to what your test results mean for common Wi-Fi uses:
- -50dBm: Excellent signal strength. You’ll rarely see better than this unless your device is directly next to the source of the Wi-Fi network.
- -55 to -60dBm: High quality signal. Devices should work well, video should stream with no issues.
- -70dBm: Low quality: Not really good enough for video, but ok for emails and web browsing
- -80dBm: Minimum signal strength needed for basic connection. Essentially unusable.
How to check Wi-Fi signal strength on an iPhone
Install the AirPort Utility from the App Store.
Open the Settings app and scroll down until you see Airport Utility. Tap on it, then tap Wi-Fi Scanner to enable this feature.
Now run AirPort Utility and you should see a blue Wi-Fi scan option at the top-right. Tap Scan and you’ll see all the Wi-Fi networks in range of your iPhone.
As continuous scan is the default, the values will change over time. You can adjust the Scan Duration slider so the results only update for the period you set.
Look at the RSSI value of your own network (which may not be top of the list) and check the value.
If you’re close to the router or whichever device is producing Wi-Fi, it should be nice and strong.
Move to the position where you want the signal to be good and see if the value is -65dBm or better. This is what you need if you’re installing, say, a Wi-Fi video doorbell or security camera.
How to check Wi-Fi signal strength on Android
On Android, download the Wi-Fi Speed Test app. It’s a favourite of ours because it’s also a handy way to test the connection speed between your phone and your router, not your broadband speed.
However, here it’s useful because it reports signal strength.
Unlike Airport Utility on an iPhone it won’t show you a list of all Wi-Fi networks in range, only the one your phone is connected to. Since you’re probably interested in only your own home Wi-Fi network, this isn’t a problem.
Just make sure your phone is connected to the right Wi-Fi network and open the app: the signal strength is displayed at the top and will change as you move around with your phone.
There are two tabs - something that's not obvious - and you can see Wireless Network Details if you swipe right from the main screen. The information here doesn’t change, but you can tap Refresh at the bottom when you move to a different location. It can be useful as it tells you whether you’re connected via 5GHz or 2.4GHz: many routers and mesh Wi-Fi systems combine the two bands and switch automatically.
The reported link speed may be useful to you, as it will give an idea of the maximum speed in that location, though as you'll see it will vary over time. Remember, too, that 2.4GHz Wi-Fi has a longer range than 5GHz.