How To Check The Actual Signal Strength On Your iPhone

In case you didn’t know, it is possible to see the signal strength indicator in numbers instead of signal bars on any iPhone (except the original iPhone) without jailbreaking it and it’s reversible.  It has been one of the old hidden features that works on the iPhone running iOS 4.1 or later.

It’s a lot more useful to see the signal strength indicator as a number [in decibels(dBm)] rather than as a signal bar (after we explain how to read the number a little bit later).

The trick is to enter the Field Test mode on the iPhone and use the trick to force quit an app to exit it.

Here’s how to change the signal strength indicator with a number rather than a signal bar:

  • Launch the Phone app
  • Dial *3001#12345#*
  • Then tap on the Call button, which will launch the Field Test app (or enter the field test mode). You’ll also notice that the signal strength indicator has switched to a number from the traditional signal bar.
  • Now hold the Power button until the red slider (slide to power off button) appears.
  • Release the Power button and press the Home button until the Field Test app quits
That’s it. You’ll notice that the signal strength indicator continues to be displayed as a number. You can now tap on the indicator to toggle between the signal strength bar and number. You can revert the changes by restarting your iPhone entering the field test mode again and exiting the app as you do normally.
 If you’ve any problems, check out the video below:
Folks at OSXDaily explain how to read the field test signal strength indicator number:

[T]he lower the number (in other words, the more negative) the worse the signal, and the higher the number (less negative) the better.

Anything above -80 is good, and would be considered full bars

Anything below -100 is bad, and would be considered few bars

For example, a signal number of -105 is considerably worse than a signal of -70. You’ll generally find that anything approaching -100 or lower is fairly bad reception, while anything above -80 is usually good, and if you tap the number signal it’s usually shown as full bars. The full range of the signal numbers extends from -40 to -120, with -120 being a nearly impossible number to see because it means no reception, and -40 would be about the strength you’d get being right alongside a cell tower.

You may find this trick useful when you’re in a dead zone and need to find a place with better signal.

So if you plan to try it out, let us know your results in the comment section below.

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  • Maxie Kalinowicz

    Works great! Running an iPhone 5 on iOS 6.0.1
    Interesting to note that apple hasn’t made the field test app “full screen”. It’s still sized for older generation devices

    • iPhoneHacks


      We noticed that too, strange that Apple hasn’t updated their internal apps for iPhone 5′s taller display yet.

      • Andrew

        They might not have changed it because your average iPhone user would never have a need to enter field test mode. Only jailbreakers and techies like us do this stuff.

      • Rounak Jain

        not enough dogfooding? :)

  • Keith

    Kinda cool to see the numbers. Thanks. However, I find signal strength is rarely the problem on AT&T. Lots of bars, just no service. In Chicago a week ago I consistently had 4 or more bars, but could never do anything with data. The 3G network is just overloaded.

  • banyoo

    well, restarting the iPhone will *not revert* that setting…

    • iPhoneHacks

      Strange, thought it worked when we tried.

      It looks like you need to enter the field test mode again and exit the app like you do normally to revert the changes. We’ve updated the post. Thanks for pointing it out.

  • Goze

    bummer only 4 iphone :(

  • Alfonso Rodriguez

    Works on iPhone 5. And you just have to Open Phone App and dial *3001#12345#* one more time And then hit Home to Revert to Signal Bars.

  • CBR900RR

    You can also tap the signal strengh to toggle between numbers and bars after the hack.

    • Zombie Killer

      swipe works better. it allows you to change back and forth

  • pingy

    hummm i can’t seem to get my i5 to work. followed the steps from above but it revert back to the bars everytime.

  • Astig_808

    at the last step try holding the home button down.thats how i got mine to work

  • Brett Mickelson

    works great on 4s

  • Erza Scarlet

    It is decibel milliwatt (dBm) describing received signal strength received by MS from BTS..just wikipedia it

  • Kiwiholden

    Gets annoying pretty quick

  • DanO

    Wow I’m glad I found your site, this is awesome, I have wanted to do this for a LONG time.

  • Emi

    Thanks this is awesome

  • TurboZ

    Hold down the home button when ACTIVATING signal number field, but just quick click of home button when you’re ready to deactivate this feature. That turned mine off.

  • Albert Pang

    Any equivalent mode on the iPad?

  • Tahir Ahmed

    Works for me. Thanks!