What’s My Cell Signal Strength?

Is your cellular signal good or poor? We’ll tell you how to find out.

Woman looking at her iPhone

Updated July 6, 2020

What do signal bars mean?

Android smartphone screen with signal bars circled

Signal bars are usually not an accurate measurement of the strength of the signal your cell phone is receiving. While they do indicate the strength and quality of your reception, there’s no industry standard for “this much signal equals this many bars”—each cell phone manufacturer uses their own calculation. When placed next to each other, two different brands of phones on the same cellular network might display different numbers of bars.

Take a look at the notification bar at the top of this Android smartphone screen: The signal meter (circled in red) indicates 4 bars. Most people would say that’s very good signal. But is it?

How cell signal strength is actually measured

The signal your phone receives from a cell tower is measured in decibel-milliwatts (dBm), a unit of electrical power in milliwatts (mW) expressed on a decibel (dB) scale. There are the three things you need to know about decibel-milliwatts:

  1. 1 milliwatt (1 mW) is equal to 0 decibel-milliwatts (0 dBm). Since cell phones receive and transmit using much less power than 1 milliwatt (often as low as 0.00000000001 mW or less), cell signal strength is less than 0 dBm and therefore measured in negative numbers.
    The closer you get to 0 dBm, the stronger the signal; for example, −70 dBm is stronger than −90 dBm, −95 dBm is stronger than −105 dBm, and so forth.
  2. The decibel-milliwatt scale is logarithmic, meaning that every 10 dBm is a tenfold change in mW:
    Power (dBm)
    Power (mW)
    −50 dBm
    0.00001 mW
    −60 dBm
    0.000001 mW
    −70 dBm
    0.0000001 mW
    −80 dBm
    0.00000001 mW
    −90 dBm
    0.000000001 mW
    −100 dBm
    0.0000000001 mW
    −110 dBm
    0.00000000001 mW
    −120 dBm
    0.000000000001 mW
    Therefore, −80 dBm is 10 times the signal strength of −90 dBm, 100 times that of −100 dBm, and 1,000 times that of −110 dBm.
  3. Any change in signal strength—gain or loss—is indicated in decibels (dB). If your outside cell signal strength is −110 dBm, and you use a cell phone signal booster in your car that provides 50 dB of gain, you’ll receive −60 dBm of signal* (−110 + 50 = −60).

* Plus any signal gain from antennas, minus any signal loss from coax cables and separation between your phone and the booster’s inside antenna.

What’s considered “good” cell signal?

4G and 5G cellular signal strength are measured using RSRP (Reference Signal Received Power). Excellent signal strength on the RSRP scale is anything stronger than about −85 dBm; poor signal strength is anything less than −115 dBm:

RSRP (dBm)
Signal strength
−80 dBm
Excellent
−90 dBm
Very good
−100 dBm
Good
−110 dBm
Fair
−120 dBm
Poor
−130 dBm
None

If you’re receiving less than −120 dBm RSRP, you’ll probably have difficulty making phone calls, sending or receiving text messages, or using internet data.

Another factor to keep in mind is the quality of your cellular connection—how much usable signal you are receiving vs. the amount of noise (unwanted disturbances of the signal). There are ways to measure cellular signal quality (RSRQ and SINR), but that’s beyond the scope of this article. Just be aware that you can have strong cellular signal but still have slow data and dropped calls because your signal quality is low.

How do I determine my cell signal strength?

Finding the signal strength received by your phone depends on the manufacturer, the phone model, and which cellular network you’re using.

Android instructions

If you have an Android smartphone, check in the phone’s settings under Signal Strength.

Exactly where this is found varies between phone models, but it’s usually somewhere in Settings > About Phone or Settings > System > About Phone. Some possible locations include:

  • Settings > About Phone > Status > Signal Strength
  • Settings > About Phone > Status > SIM Card Status > Signal Strength
  • Settings > System > About Phone > Status > SIM Status > Signal Strength

Here are some examples from Android phones in our office. (Notice that the RSRP readings in dBm are all nearly identical, but the number of bars varies.)

(click images to enlarge)

Signal strength reading on a Samsung Note 9 with Android 10 Signal strength reading on a Motorola Moto Z2 Play with Android 8 Signal strength reading on a Motorola Moto Z2 Play with Android 6

There are also many Android apps in the Google Play store that will display your phone’s signal strength. One that we recommend is Network Cell Info Lite, a free, ad-supported app that shows your RSRP signal strength on its dashboard-like Gauge screen:

Links to third-party software are provided “as is,” without warranty of any kind, either expressed or implied, and such software is to be used at your own risk. Powerful Signal will not be liable for any damages that you may suffer in connection with downloading, installing, or using such software.

iPhone instructions

Getting the cell signal strength reading on an iPhone may be possible if your carrier and the chipset in your phone both support it.

Dial *3001#12345#* and press the Call button:

Dial *3001#12345#* to put an iPhone into Field Test Mode (iOS 11)

This will put your iPhone into Field Test Mode. You’ll see one of the three screens below:

If your Field Test Mode screen looks like this:

Tap 1xEV-DO.
iPhone iOS 11 Field Test Mode screen for Qualcomm chips on Verizon or Sprint
On the next screen, look for the reading next to Rx AGC0.
iPhone iOS Field Test Mode 1xEV-DO screen for Qualcomm chips on Verizon or Sprint

To exit Field Test Mode, tap the left arrow icon in the top left-hand corner of your screen.

If your Field Test Mode screen looks like this:

Tap LTE.
iPhone iOS 11 Field Test Mode screen for Intel chips on AT&T or T-Mobile
On the next screen, tap Serving Cell Meas.
iPhone iOS 11 Field Test Mode LTE screen for Intel chips on AT&T or T-Mobile
On the next screen, look for the reading next to rsrp0.
iPhone iOS Field Test Mode Serving Cell Meas screen for Intel chips on AT&T or T-Mobile

To exit Field Test Mode, tap the left arrow icon in the top left-hand corner of your screen.

If your Field Test Mode screen looks like this:

iPhone iOS 11 Field Test Mode screen for other chipsets and carriers

Unfortunately this combination of chipset and carrier does not allow you to get a cell signal reading in dBm. You’ll have to take a signal reading with another iPhone, an Android phone, or a signal meter.

To exit Field Test Mode, tap the left arrow icon in the top left-hand corner of your screen.

Your cell signal will fluctuate

The signal strength you receive from the cell tower will continually increase and decrease, even if you’re not moving. Standing still, you’ll commonly see fluctuations of ±5 dB. This is mainly due to user load on the cell tower—the tower antenna’s power has to be spread across all the connected devices. Peak usage times (rush hour, lunch hour, etc.) can result in noticeably lower power for all users.

Because of shifting usage loads, signal strength from a cell tower to your phone is constantly changing. If your cell signal is −110 dBm RSRP, you can probably make a call without any problems. If your −110 dBm signal falls to −120 dBm RSRP because of the load on the tower, you might drop a call but be able to redial and reconnect in a few seconds.

Physical barriers block cellular transmissions

It’s possible to be close to a cell tower but still receive weak cell signal. Many building materials—including concrete, metal, low-e glass, wood, and plaster—reflect or absorb cellular frequencies, preventing them from penetrating the building and reaching your phone. Stucco with wire mesh, metal roofs, large logs, and vapor barriers in attics also impede cellular signal. A large concrete building between you and the cell tower can also block signal from reaching you.

If you’re outdoors, dense forest and hills will reduce or block cell signal. Low areas around lakes, rivers, and gullies can also experience problems—there is signal, but it’s passing way over your head.

Dense urban areas with tall buildings have a different set of problems: Sometimes the top floors of buildings, forty or fifty stories up, can’t get reliable cell signal because cell tower antennas are aimed at lower elevations.

In these situations, a cell phone signal booster for home, office, or vehicle can solve your reception problems.

I can see the tower, but I have no signal

Sometimes you can see your carrier’s tower down the road or off in the distance, but you still have weak cell signal. However, just because you can see the tower doesn’t mean that the tower is broadcasting in your direction. This type of issue is more common along remote highways where cell signal is mostly directed toward the highway and little or none is directed behind the tower.

The sector antennas used on cell towers broadcast signal only in certain directions. Just because you can see the tower does not mean that it sees you.

It’s also possible that the tower nearest to you is owned or leased by a different carrier than the one you’re using.

Frequency and technology limitations

Different cellular frequencies are able to travel different distances. Cellular transmissions in lower frequency ranges (700 MHz LTE and 800 MHz CLR) can travel more than twice the distance of transmissions in higher cellular frequencies (1900 MHz PCS and 1700/2100 MHz AWS).

Relative range of low-band cellular frequencies Current low-band cellular frequencies can travel long distances, with the lowest frequencies having the longest ranges. (Click to enlarge.)

Slower, low-frequency transmissions also penetrate building materials better than faster, higher-frequency transmissions. You might be able to get slower cellular service at 700 MHz inside a large, downtown building, but not get any faster PCS or AWS coverage because the higher-frequency bands can’t get through the building’s concrete exterior.

If you can determine which frequencies your carrier uses in your area, you might be able to discover the reason behind the reception issues you’re having. (Powerful Signal can help you with this; give us a call or email us for help.)

Call Powerful Signal at 866‐912‐3444

…or contact us online. Our experts can help you determine why your cell phone signal may not be as strong as you need and help you find a solution to your problem.