Use Field Test Mode to See True iPhone Signal Strength as Numbers Instead of Bars

Aug 20, 2012 - 28 Comments

iPhone cell signal bars are shown as numbers rather than bars with Field Test mode

Field Test Mode is a hidden feature on the iPhone which allows you to see technical details of the device, the most useful of which is the true signal strength displayed as a number rather than the traditional signal bars. We’ll show you exactly how to enable Field Test Mode to be able to see the real cellular signal from your iPhone, and also how to read the numbers so that you can understand what is a good cell signal vs a bad one. It only takes a minute or two, and it’s easy to reverse back to normal, so try it out!

Entering Field Test Mode on iPhone

This will work on any iPhone model except the original:

  • From the iPhone keypad, dial *3001#12345#* and hit “Call”

Enter Field Test Mode on iPhone by dialing these numbers

You will immediately see the signal numbers in the upper left corner, and you can tap around the menus to discover other random features and information that is generally meaningless outside of cell technicians and field operators. If you hit the Home button you’ll quit out of Field Test and the signal indicator will return to bars rather than the signal numbers, but it’s easy to always see the numbers too as described below.

Enabling Signal Number as Reception Indicator Rather Than Signal Bars

To always see the signal numbers rather than the signal bars, you’ll use the Force Quit app function to kill Field Test when it’s open:

  • Dial *3001#12345#* and hit “Call” if you haven’t done so already to launch Field Test
  • Now hold down the Power button until the “Slide to Power Off” message appears, then release the Power button and hold the Home button until Field Test quits
  • Tap the signal bars or signal numbers to switch between the two

To remove the tap-to-switch signal indicator ability, you can either reboot the iPhone or go back into Field Test and close out of it as usual.

How to Read the Field Test Signal Indicator Numbers

The numbers don’t follow a scale that makes much sense to normal people, but the 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 -105 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 -130 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. Technically, the number goes all the way to -140, but you will almost never see that because it basically means there is no signal to speak of, and most users will see -120 or -130 before it switches over to the “No Service” indicator instead.

Once you get the hang of reading the numbers, you’ll find it’s much more accurate, and it becomes easier to predict when you may drop a call or start to get a bad signal or connection, which creates the weird artifacts and sounds on phone calls, often before it starts to cut out or even drop completely. That typically starts happening around -110 or so, before dropping the connection or call completely if it hits -120 to -130.

If you’re having any problems getting this to work, or you want to see how to do this yourself before jumping in, watch the video below:

This is actually a fairly old hidden feature that works on any iPhone running iOS 4.1 or later, but we’ve had a lot of questions about it recently due to several recent iPhone tip screenshots showing the signal numbers. Basically all of us here at OSXDaily have these signal numbers shown full time on our phones for a variety of reasons, and so you will commonly see them in articles around here.

For those who use Personal Hotspot often, or just for the geekier folks among us, it can be fun to test the mobile download speeds using apps like Speed Test with these signal numbers visible, because it can help to find optimal signal locations and device placement for the best possible speeds.

Enjoy this tip? Subscribe to the OSXDaily newsletter to get more of our great Apple tips, tricks, and important news delivered to your inbox! Enter your email address below:

Related articles:

Posted by: William Pearson in iPhone, Tips & Tricks

28 Comments

» Comments RSS Feed

  1. Avenged110 says:

    Just for fun, you can also keep the numerical value indicator even after exiting FTM. While in field test mode, hold the sleep/wake button until the shutdown slider comes up and then hold the Home button until the hidden app is force quit and you are returned to the Homescreen. The numerical value will remain in the status bar. To return to bars simply tap or re-enter FTM.

    Also FWIW I show -47 when using my M-Cell.

    • Grant says:

      Great tips here. What I think is amazing is how generous Apple is when reading the signals and interpreting that as full bars when for data transfer it can be a 1MB/s difference!

      And yes, the absolute maximum signal is -40 and that is basically if you are next to a cell tower or a microcell.

      • Zebediah says:

        -110 or up and you’ll start losing the call, -120 is not visible because there would be no reception.

        If you have an iPhone 4 you can bridge the antennas in the corner and force the phone into the -110 to -120 range, the whole “Antennagate” thing was real.

        • Avenged110 says:

          Ftr, I have an iPhone 4 on AT&T and I can only get it to drop about 1 bar when bridging the antennas. I don’t use a case and have never had any issues which surprised me, considering I’m left handed and always death grip it…

  2. Jimmy says:

    Thanks for posting this. Is there a way to monitor 3G strength? Frequently, on Verizon, I have 3 or 4 bars of signal but 3G drops out completely.

    • Avenged110 says:

      Well technically this would track the strength of the signal being received by your phone which, assuming cell data is on, would consist of both CDMA and EVDO since they’re not really separate like Wi-Fi. Correct me if I’m wrong because I think I am.

  3. Richard says:

    All I got was “Error performing request. Unknown error.” Tried it three times to be sure I dialed correctly.

  4. Richard says:

    Never mind. I missed the last * after the last #.

  5. Mike Stead says:

    Garbage.

    The bars are a QoS score not a signal strength score. In 3G networks it is possible to have very poor call quality with strong signal strength, and a perfectly good connection at very low signal strengths.

    3G is all about dominant-to-interfering carrier ratios. Suggesting this gives a more accurate idea of call quality is fundamentally incorrect.

  6. Andy Matheson says:

    Does this work in the UK?

  7. Arthur says:

    Does it exist for android ? ^.^

  8. Ben says:

    This has been most useful to me over the last few weeks. Our reception is -45 a few hundred metres away, drops to -65 a hundred metres away then right down to -100 to -116 in or outside our house.
    Next to impossible to make a call for more than a couple of minutes. Telstra doesn’t care.

  9. vdiv says:

    Aaaah, numbers… But what do they really mean?

    http://en.wikipedia.org/wiki/Decibel

  10. evge says:

    I can’t seem to get rid of the bar at the bottom that showed up that covers the names at the bottom of my home screen. Any ideas besides whats been listed here.

  11. frank says:

    This is great for 3G but what about wifi? I’d like to be able to get the reading on my iPad/iPhone on how good my wifi signal is…

  12. SmashDanny says:

    Is there a way to disable this ?

    • Koen says:

      I assume you have force quit Field Test to show numbers instead of bars. To go back to bars you just need to re-open Field Test and everything will go back to normal.

      • SmashDanny says:

        No that didn’t worked. I tried it just with pressing the home button and with force quit. Also restarted my iPhone.

        • Wicho says:

          Just tap the Numbers and switch between Bars or Numbers. ;-)

          • SmashDanny says:

            It automatically switches from Bars to Numbers. For Example I open WhatsApp and the Bars change to Numbers. Then I tap on the Numbers change it to Bars, but maybe after 2 minutes it switches again.

  13. alaskan master says:

    -34 is the signal that you will see standing right in front of a UMTS sector (4G tower)

  14. kJohns says:

    Seems to be patched in 7.0.3 in the iPhone 5S.. FTM simply restarts.

    • whatwhy says:

      I am using field test now with iOS 7.0.4, it works fine though you may need to tap the bars again to re-enable it sometimes.

    • Anonymous says:

      I have the same problem with my iPhone 4S running iOS 7.0.4.

      • Pal says:

        Field Test Mode continues to work with all iPhone models running iOS 7.0.4, since it is used for testing it will probably always be possible to enable.

        Remember to tap on the little signal dots (rather than bars now) to switch between the Field Test Mode and the normal cellular strength signal.

  15. guy from poland says:

    Is it somehow possible to do the same on iPad? Specifically: iPad Mini Retina.

  16. Anonymous says:

    This works on jailbroke iPhone for the WIFI strength, phone set to airplane mode, with SBSettings installed, and the option turned on to display these numbers inside SBSettings!!! Doing such, I can get the number to even reach -20 holding the phone Right Next to the WIFI Access Point. This will be very handy when diagnosing networks @ work. Thank You for explaining what the numbers mean!!! :) …Cheers!!!

Leave a Reply

 

Shop for Apple & Mac Deals on Amazon.com

Subscribe to OSXDaily

Subscribe to RSS Subscribe to Twitter Feed Follow on Facebook Subscribe to eMail Updates