This is a very old trick but a nifty one to figure out how strong the signal is on your iPhone. A simple ‘Field Test Mode’ will help you toggle the signal strength bar into numbers that show how strong the signal really is.

The signal bars are good indicators themselves but the numbers are a far more accurate representation.

Here’s a short trick that will change the signal bars into numbers.

How to See the iPhone Signal Strength in Numbers Without Jailbreak

How to Enable Field Test Mode to Change Signal Bars to Numbers

  • Open the Phone app
  • Dial this number: *3001#12345#*
  • Call

How to Change Signal Bars to Number Indicator on the iPhone Without Jailbreak

A new screen opens up. This is called the ‘Field Test Mode’. As it happens, you’ll notice that the signal bars have changed into a (negative) number. This is the actual signal strength of the network that your iPhone connects to.

If you tap the signal strength number, it changes to bars. Tap again and you get the numbers. It’s a tap-to-toggle here.

How to Check the Actual Signal Strength

The signal strength usually fluctuates between -100 and -70 but can vary vastly depending on your location and the real strength of the signals your iPhone is receiving. The closer the number is to zero, the stronger the signal is.

The unit of signal strength is dBm. There’s a ton of info about the unit and the average values for various types of communications here.

How to Revert Back to Signal Bars

Just press the home button and the iPhone will snap out of Field Test Mode. The signal bars will toggle back on.

If you want to have the tap-to-toggle feature permanently enabled, you can easily achieve it by following this:

  • Open the Phone app
  • Dial *3001#12345#* and tap Call
  • In the Field Test Mode, press the power button till the ‘slide to power off’ shows
  • Don’t slide. Just press the home button for as long as it takes to close the slider.
  • The Field Test Mode will exit but the signal strength indicator will remain in numbers. Tap to toggle the indicator to bars and back to numbers.