Use Field Test Mode to See True iPhone Signal Strength as Numbers Instead of Bars
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.
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”
You’ll 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 -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.
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 tip screenshots showing the signal numbers.
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.
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.
-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.
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…
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.
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.
All I got was “Error performing request. Unknown error.” Tried it three times to be sure I dialed correctly.
Never mind. I missed the last * after the last #.
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.
Does this work in the UK?
Should work on every iPhone regardless of carrier, but you will have to try it to find out for sure.
Does it exist for android ? ^.^
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.
Aaaah, numbers… But what do they really mean?
http://en.wikipedia.org/wiki/Decibel
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.
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…
Is there a way to disable this ?
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.
No that didn’t worked. I tried it just with pressing the home button and with force quit. Also restarted my iPhone.
Just tap the Numbers and switch between Bars or Numbers.
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.
-34 is the signal that you will see standing right in front of a UMTS sector (4G tower)