Real Signal Strength on an iPhone

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 entering the field test mode again and exiting the app as you do normally. How To Check The Actual Signal Strength On Your iPhone

Tap the signal bars or signal numbers to switch between the bars and the actual signal strength. Use Field Test Mode to See True iPhone Signal Strength as Numbers Instead of Bars

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