Find the Signal Strength of Your iPhone using Field Test Mode

October 6, 2015 — by KEN PERKINS


Field Test Mode, iPhone signal strength


A few weeks back I posted about finding the signal strength in decibels (dBm) on an Android phone, and I promised then to post similar instructions for finding signal strength on iPhones. So here we go.

It’s often useful to know how strong a signal your iPhone is receiving. As pointed out previously, if you’re trying to make a call but it won’t go through or if you’re otherwise not getting the cell service you expect, then knowing your signal strength can help you determine why not.

Of course virtually all phones have the “bars” or “dots” graphic that displays on your home screen, supposedly so you know what your cell phone signal strength is. The problem with that graphical representation is that it lacks any kind of standards.

The accuracy of the dots can vary widely, so viewing your iPhone’s actual signal strength reading is always preferable to relying on the dots graphic. Signal strength is typically measured in dBm, a standard unit of measure. By accessing the decibel reading on your iPhone you know with certainty how strong a signal you are receiving.

While Android phones allow the user to view signal strength readings by navigating the menu tree, with iPhones finding the decibel reading is a bit more complicated. You must enter a sequence of commands to put your iPhone into ‘Field Test’ mode to display the dBm reading.


If you have updated your iPhone to iOS 9, follow the instructions directly below. These instructions are specific to iOS 9. If you’re using an earlier version of iOS, those Test Mode access instructions are further down in the post.

  1. Dial *3001#12345#*
  2. Press CALL
  3. Hold the power button for about 5-7 seconds until you see the “slide to power off” screen.
  4. Do NOT power off the phone!
  5. Hold the home button (round button at the bottom) for about 5-7 seconds.
  6. It will return you to the home screen and the decibel reading will be at the top of your screen.


dBm is typically expressed as a negative number, -88 for example. The closer to zero the reading is, the stronger the cell phone signal. So for example, -79 dBm is a stronger signal than -88 dBm. A reading of -50 is the strongest signal you will see. When a signal is weaker than -100 dBm, that’s a pretty weak signal. If the signal gets much weaker than that, you likely won’t have service.

If you don’t want the dBm reading to display on your iPhone home screen, you can dial the sequence again and just hit “back to phone” and it’ll return to the dots graphic.


The instructions below have worked for iPhone 5 models and newer up until the iOS 9 release.

  1. go into Settings, then Cellular
  2. turn OFF the LTE.
  3. From your phone’s keypad, dial *3001#12345#* and press the CALL button.

Your screen will show “Test Mode” and the dBm reading (as a negative number) will display in the upper left side of your screen.


Did you like this post? Find it helpful? Do you have questions about this topic? Please let us know how we’re doing by commenting below.


Related Posts:

Find The Signal Strength of Your Android Phone

Why Do I Have Such Poor Cell Phone Reception?

Apps for Finding Cell Towers

How to Extend Cell Phone Range in the Middle of Nowhere


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    Comments (5)

    Don on December 15, 2015 at 2:12 am said:

    What is LTE? I’m trying to follow your instructions for checking my signal strength. I have an I-phone 4S. I can”t find where to turn off LTE

      weBoost Customer Support on December 15, 2015 at 6:49 pm said:

      If you are using an iPhone 4S (or older) you will not need to turn off LTE, as this is not a function of the phone. You can ignore this step and go straight to your phone and dial ” *3001#12345#* ” and press the CALL button. If the next screen does not show the negative number in the top left-hand side of the screen, drag down the top Notification bar and you should see the negative number appear on that new screen.

    Janet Schlichting on March 3, 2016 at 5:37 pm said:

    I tried all these options. My iPhone says Field Test. under that is has a line that says 1xEV-DO and another that says 1x. how do I find my signal strength?

    weBoost Support on March 3, 2016 at 6:44 pm said:

    Thank you for your question, Janet Schlichting. With updated iOS systems, you may need to swipe the phone screen from top to bottom, dropping down your notification bar. This should then allow the negative number to appear in the top left hand corner. For additional questions and help, you can reach us here:

    weBoost eqo Cell Phone Signal Booster Review - One Bar No More on June 20, 2016 at 8:50 pm said:

    […] Here are the step-by-step instructions for how to turn those cell signal bars into a number measured in decibels (dBm) that more precisely indicates reception strength. -50 is about the strongest you will ever see, with -100 being on the very low end of the spectrum, going as low as -115 (almost no service at all). This is the first step in setting up the weBoost eqo cell phone signal booster. Once you’ve made that change, your top bar will look something like this: […]