Signal bars don’t tell you as much as you think. If you really want to know the strength of your cell signal, use this hidden app.
We’ve become reliant on signal bars to tell us how strong our cellular connection is, but the bars are not accurate. Every phone manufacturer gets to decide how much signal strength equals how many bars, and it often varies widely from model to model.
If you really want to know how strong your cell signal is, you need to look at a direct measurement of the signal strength, as measured in decibels (dB). Fortunately, there’s a hidden “Field Test” menu on your iPhone. This guide should work for anyone on iOS 11 or iOS 12.
How to access the Field Test menu
First turn off your Wi-Fi before accessing the Field Test application.
Open the Control Center (or launch the Settings app) and turn off Wi-Fi.
Open the Phone app and enter in the following numbers and symbols:
Press the call button, and the Field Test menu will pop up on screen.
There’s a lot to check out in here, and it’s not very well labeled. After all, this is not a menu for regular users, but for service technicians.
Select “LTE” from the first menu.
Now, select Serving Cell Meas.
Selecting Serving Cell Meas will take you to a page of data. You’ll notice the order of the listing here changes every few seconds, as the measurements continually update.
You’re looking for “rsrp0,” which is the Reference Signal Received Power for the tower closest to you (although you may be connected to a secondary, further tower, whose power is listed under “rsrp1”).
The figure you should be most concerned with is rsrp0.
This should be a negative number, in a range from around -40 to -140. A number closer to -40 is a really strong signal, while a number closer to -140 is a really poor signal. Anything between -40 and -80 is very good and you shouldn’t have any signal problems. Anything below -120 is very poor, and you might suffer interruptions in your connection and very poor data speeds.
There’s another useful data point on this page, labeled RSRQ0 (Reference Signal Received Quality). This is a value derived from both the signal strength and interference. This usually ranges between -3 (good) and -19.5 (bad). It’s possible to have a lower number, but to do so you have to have a really noisy, low-power signal.