If you ask most people about the current quality or strength of their phone’s cell signal, regardless of their carrier, and they’ll probably give you one of the following responses:
“I’m at full bars. Great coverage.”
“I’ve barely got one bar of service.”
“I’ve only got half bars right now.”
It’s an easy to understand point of reference. But it hardly provides a complete picture.
On your iPhone or Android—along with any other cellphone or cellular-connected device in between—the signal bars are mostly there to provide a visual representation of cell signal strength. The truth is, the number of bars you see on your phone can vary greatly and often depend on the manufacturer and model. And isn’t entirely representative of signal strength.
Some phones assign different values to each bar graphic. Which means the two signal bars showing on your model of iPhone may actually show that your phone is receiving more signals than your friend’s Android phone that’s currently displaying three signal bars. Just like a car’s gas gauge, signal bars can only provide a general idea of signal strength—not an exact measure.
Viewing your phone’s actual signal strength is better than relying on bars alone. However, to make sense of this reading, let’s get an understanding of how cell signal strength is measured.
Understanding Cell Signal Strength
Decibels offer a more accurate and useful measure of cell phone signal strength.
Signal strength for cellphones is calculated using dBm (or decibel milliwatts) as its standard unit of measure. On a signal strength meter, dBm is typically expressed as a negative number—such as -88. The closer to zero the reading is, the stronger the cell phone signal. For example, a signal strength reading of -79 dBm signifies a stronger cell signal than one measure at -88 dBm.
The typical range of measure for cell signal strength is between -110 dBm and -30 dBm. Being a logarithmic unit of measure, each 3-dB increase is actually doubling the power. So, a cell signal that measures -76 dBm is twice as powerful as a cell signal that comes in at -79 dBm.
On the scale of signal strength, -110 dBm is close to no signal. Between -85 dBm and -100 dBm is poor signal strength. -65 dBm to -84 dBm is a good signal. -64 dBm to -50 dBm is excellent.
In field test mode, some phones may show the dBm measure as a positive number. In situations like that, simply convert the number to a negative. For example, 60 dBm is actually -60 dBm.
How Cell Signal Works with Your Phone
Different ways you may use your phone require different cell signal strengths. To make a call, -100 dBm is not ideal but will work. It becomes more difficult to maintain a wireless data transfer at the -100 dBm range—particularly at 4G or LTE speeds. To enjoy optimal functionality on your smartphone or cellular-connected device, you’ll want a signal between -50 dBm and -80 dBm.
When your cell signal is weaker than -100 dbm, it’s likely that you won’t have service without relying on a cell signal booster. If you’re not familiar with cell phone signal boosters and how they work, this guide to cell signal boosters offers a helpful explanation on how they make stronger cell connectivity possible.
How to Test Signal Strength for an iPhone
For iPhones, there are some helpful apps that you can download to test existing cell signal strength and network speeds.
OpenSignal is a free app that allows you to run a test of your iPhone’s true speed (i.e. what you are likely to experience when normally using your phone) and view maps of real coverage in your area—while showing you which network is best in your area. It also features compass points to show you which direction your cell signal is coming from.
Speedtest by Ookla is another free app, trusted by professionals for testing connection speeds. Quick, easy, one-tap connection speed tests can take place practically anywhere because of the app developer’s extensive global network. Users can access detailed reporting on past tests and simulate downloading a file to show how signal strength really affects iPhone performance.
iPhone users can also view a signal strength reading by accessing their iPhone Field Test Mode. Below are instructions to enact the field test mode on current iPhone models, using 11.1 iOS or higher.
- Key in *3001#12345#*
- Tap : Serving Cell Measurements
- Scroll down to: Measured RSRP
- Add +20 dBm to the resulting number (example -102 shown would be -82 dBm
Legacy iPhone Field Test Mode
- Go into the Phone app
- Switch to the Keypad, as you would do to dial a phone number.
- Dial *3001#12345#* and press the Call button.
This will launch the Field Test Mode app. Where the bars at the top left corner of the screen once where, you’ll now see “< Back to iPhone”. Hold down the power button until you see “Slide to Power Off”, then release it. Then hold the Home button until you’re returned to your main app screen. You’ll now see your numerical signal strength while you use your phone, and you’ll be able to tap the signal numbers to switch to signal bars, and vice versa.
The negative number is the signal strength reading, which should be followed by the carrier name and then the network type.
To exit this permanent field-test mode, simply reboot the phone or reload Field Test Mode and exit it via the Home button. When taking signal readings, move to the location where you want to take the reading, wait for 30 to 60 seconds for the signal readings to catch up, and then record the signal strength and network type (2G, 3G, 4G, LTE, etc.).
How to Test Signal Strength for an Android
For Android users, there is a great go-to app to do a signal strength test and network speed test.
Network Cell Info Lite, available for free on the Google Play store, provides nearly real-time monitoring of cellular and WiFi signals. Raw network cellular information is provided, such as network speeds as shown in decibels. Route coloring is displayed in a map, in accordance to signal strength and relative location of towers form the Mozilla MLS database.
Most Android phone models allow the user to view signal strength readings by navigating the device’s menu tree. Accessing Field test mode on Android phones is also straightforward.
Simply find your way to “Settings” > “About Phone”, and your numerical signal strength will be available under either Network or Status, depending on the model of the phone you own. Being able to find the right menu screen varies across phone manufacturers, models and versions of Android OS. A typical navigation sequence is Settings – About Phone – Status or Network – Signal Strength or Network Type and Strength.
An alternate navigation sequence for some Android phones is Settings> More Options or More Settings > About Phone > Mobile Networks > Signal Strength. Some experimenting with the menus on your Android phone should get you a dBm reading that’s reliable.
Please note: Android phones will read only one network at a time. If you have 4G network access, that’s the default dBm reading your phone will display. If there’s no 4G service at the moment, the reading will default to 3G.
After following the instructions above, if you’re unable to determine your device’s signal strength reading, check the operations guide that came with your device. Alternatively, there are apps you can download from the Google Play Store, such as SignalCheck Lite, which allow you to read your signal strength as well. *Hint: look for the 1x or 3G signal for accurate results. *
Hence why a signal booster would be able to overcome these challenges and bring you the strong, reliable cell coverage that you expect inside your home or vehicle.
With testing cell signal strength, it’s easier to see how subtle differences in signal strength can affect the performance of your smartphone, tablets, or other cellular-connected devices. It can also be a great way to troubleshoot why you may be experiencing dropped calls, delayed texts, slow data speeds, or problems with streaming content.
Ready to improve your cell signal now? Click the button below to shop cell phone boosters.