When you look at your iPhone and want to know how strong your signal is, you see bars. You’ll see somewhere between one and five bars — one being the weakest and five being the strongest. This is a pretty vague reading, and it doesn’t give you the strongest idea of how strong (or weak), the cellular signal actually is.
First, you’ll need to put your phone into field test mode. To do so, call the following phone number: *3001#12345#* and then — while in the field test menu — hold your phone until Slide to Power Off appears.
Don’t power off your device, though. Instead, hold down the Home button until your home screen pops back up. Now, the top-left corner of your screen will display numbers instead of bars. If you want to change back to bars, just tap the area where the numbers are.
The numbers will range somewhere between -40 and -130, with lower numbers (actually higher, because we’re talking about negative numbers — -40 is closer to 0). The numbers on the far end of that spectrum are nearly impossible to get, as -40 is perfect, and -130 is zeno signal.
Generally, -80 is considered a strong signal (5 bars), and-110 is weak (1 bar).
For me, I have signal booster through my carrier, which is why you see -64 in the screenshot above. When that’s off, I get about -110, hence the need for the enhancer.
What is the actual signal number of your iPhone in your home? Let us know in the comments!