How do I Calculate Signal Strength?

Written by darnell clayton
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How do I Calculate Signal Strength?
Mobile phone operating systems include iOS, Android and BlackBerry. (Jupiterimages/ Images)

You can calculate signal strength on your cellphone by switching your phone to field test mode, which will display your signal strength using numerical dBm or decibels to the milliwatt, navigating directly to the signal strength screen or by installing a third-party app on your device that will analyse the uploading or downloading speeds of your phone. Activating field test mode on your phone differs between mobile operating systems and will result in your phone bars located near the top of your screen being replaced with a negative number. Numbers closer to zero dBm indicate a stronger signal.

Skill level:



  1. 1

    Tap on the default "Phone" app. If you are unable to locate the "Phone" app, click on the physical "Home" button, then after three seconds click on the physical "Home" button again. Type "Phone" in the search field above and tap on the green phone icon.

  2. 2

    Tap on the "Keypad" menu option below and then type in "3001#12345#" to launch the "field test program" for your iPhone and replace your phone bars with numbers representing dBm values.

  3. 3

    Tap on the dBm numbers to switch back to phone bars. If you prefer to view dBm values instead of cellphone bars, press and hold down the physical "Power" button, located near the top of the iPhone on the edge, until you see the "slide to power off" slider on the screen, but do not slide to power off the iPhone.

  4. 4

    Press and hold down the physical "Home" button until the "field test program" terminates to maintain the display of dBm numbers instead of phone bars. If you prefer to switch back to phone bars in the future, tap on the default "Phone" app, then dial "3001#12345#" to launch the "field test program."

  5. 5

    Tap on the dBm numbers to switch back to phone bars on your iPhone.


  1. 1

    Select "Menu" on your Android device, then navigate and tap, or select with your scroll ball, "Settings."

  2. 2

    Select "About" and then tap on, or select with your scroll ball, "Phone."

  3. 3

    Select "Status," which will reveal the signal strength on your Android device. To activate the field test program on Android instead, tap the "Phone" app, then dial "##4636##" and then select "Phone Information." Phone Information will provide you with more details regarding the strength of your cellphone.


  1. 1

    Tap or select with the scroll ball the "Tools" option. On select BlackBerry devices tap or select "Options."

  2. 2

    Select the "Settings" option only if you had to previously select "Tools" in the last step. If you selected "Options," then skip this step.

  3. 3

    Select the "Status" option, which will replace your phone bars with dBm numerical values.

    Using Third-Party Apps

  1. 1

    Navigate and open your respective application store, which will be labelled as "App Store," "App Market" or "App World" on your screen.

  2. 2

    Type in "speed test" in the search field. Read the descriptions of the third-party apps to verify that the app measures Internet speed from your device.

  3. 3

    Select the third-party app and then tap on "begin test" or "start" to initiate the speed test of your phone, which will calculate how many Mbps (or megabytes per second) your phone was able to upload and download to a remote server.

Tips and warnings

  • If you are measuring cell signal through a third-party app, verify that your Wi-Fi settings are turned off to ensure that your cell signal strength is accurately measured.
  • Activating field test mode on your cellphone should only be done by a professional or if you are following steps outlined within the user manual of the phone.

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