If you've ever found yourself wandering in circles or leaning halfway out your bedroom window to find a few bars, you can kiss those days goodbye. Bars are not exactly accurate — some phones, like iPhones, have five bars, while others, like Nexus One, only have four. Three bars for T-Mobile may be equal to two bars for Verizon. Having a bad signal is almost as annoying as running out of storage space, but it can be near impossible to find the best signal when you're not even sure what kind of signal your bars indicate.
Rather than using bars, iPhones and Androids can actually tell you exactly how strong your signal is using decibels instead, with lower values indicating a stronger signal. Full bars equate to -50 decibels (or dB), representing great signal, while -110 dB is virtually no signal, or a dead zone. If you're frequently experiencing dropped calls, lost connections, and very slow internet, chances are you're near a dead zone.
Here's a handy chart for reference on what the numbers mean:
- -90 or higher = Excellent
- -91 to -105 = Good
- -106 to -120 = Fair
- -121 to -124 = Poor
- -125 = No Signal
To find your decibel reading, you'll want to enter Field Test Mode. Field Test Mode works for any models of iPhone and any version of iOS, expect for the original. You might want to turn off WiFi (Settings > WiFi) and LTE (Settings > Cellular > Enable LTE), as readings can be different from standard cell phone signals.
For iPhones using iOS version 10 or earlier, access the Field Test Mode by typing *3001#12345#* in the phone's keypad and pressing dial. This will bring up the Field Test menu.
In the top left corner, you will see the dB reading (shown as -99 in the above photo). To keep your signal display in dB, hold down the Power button until the "Slide to Power Off" message appears while still in Field Test Mode, then release the Power button and hold the Home button until Field Test quits. You can now toggle between signal "dots" or signal numbers by tapping the upper left hand corner, and you can move room to room to see where your dB reading is the lowest (which means the signal is the strongest). To go back to normal, go back into Field Test Mode, then quit it normally by pressing the Home button.
For iPhones using iOS version 11 or later, access the Field Test Mode by dialing the same code (*3001#12345#*), selecting LTE, and then Serving Cell Meas. Your dB reading will be shown next to rsrp0.
For Android phones, enter "Settings," then select "About Phone." Your signal strength in dB will be displayed under "Network" or "Status." An alternate navigation sequence for some Android phones is Settings > More Options or More Settings > About Phone > Mobile Networks > Signal Strength.
If you're trying to determine where your dB reading falls, -80dB or higher is generally considered a strong signal, whereas -110dB or lower is generally a very weak signal. That number can vary anywhere from -40 to -130, but the closer it is to zero, the less frustration you're likely to experience. If your signal needs some assistance, you can always invest in a cell signal booster to get a better reading.