Because Wi-Fi uses radio waves to transmit and receive data, it’s invisible. That probably sounds like an odd thing to say, as well as patently obvious, but the point is that you can’t tell very easily whether you have a strong Wi-Fi signal in all parts of your home.

You won’t know whether slow internet problems are due to a weak Wi-Fi signal or not, and while running internet speed tests can highlight broadband problems, knowing the exact Wi-Fi signal strength can be very useful when you’re deciding where to place your router, your mesh Wi-Fi satellites and even devices such as outdoor security cameras.

And the good news is that you do this for free on any iPhone or Android phone. Read on to find out how.

What's a good Wi-Fi signal strength?

Before we get to the steps, it’s important to know what the numbers mean, otherwise you’ll still be in the dark. Signal strength is expressed as a percentage or, more commonly an RSSI value in dBm. RSSI simply stands for received signal strength indicator, and is what the apps below will show you.

The closer the value is to 0, the stronger the signal is. Things are slightly confusing 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 the numbers 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. Anything you can do over Wi-Fi will work well.
  • -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 at any quality, 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 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.

How to check Wi-Fi signal strength

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.

How to check Wi-Fi signal strength

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.

How to check Wi-Fi signal strength

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’ll want if you’re installing a Wi-Fi video doorbell or security camera.

If not, check our tips for improving Wi-Fi signal. You may have move your router, or invest in a better one – or a mesh Wi-Fi system.

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 a handy way to test how fast the connection is between your phone and your router, not your broadband speed.

However, here it’s useful because it also reports signal strength.

How to check Wi-Fi 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: 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.

Related articles for further reading