How to Check Your Cell Signal Strength in dBm (and What the Numbers Mean)
Short answer
Signal bars are a rough summary that varies by phone maker, so check the number instead. On most Android phones it is under Settings, About phone, then Status or SIM status, shown in dBm; iPhones hide it in Field Test Mode. For LTE and 5G signal strength (RSRP), better than −90 dBm is good, −90 to −100 dBm is fair, −100 to −110 dBm is poor, and below −110 dBm is effectively no usable service.
Updated
Why Signal Bars Don't Tell You Much
Bars are each phone maker's simplified summary of the signal, and the scale behind them differs between manufacturers and carriers. Two phones in the same spot can show different bars, and a phone can show full bars while data barely moves, because bars mostly reflect signal strength and ignore interference. The number behind the bars, measured in dBm, is the same kind of value on every phone, so it is what to compare.
How to See Your Signal in dBm
Android
On most Android phones: Settings → About phone → Status (or SIM status), then look for Signal strength. On Samsung phones it is under About phone → Status information → SIM card status. The exact path varies by manufacturer and Android version. On LTE and 5G, the dBm figure shown is usually the RSRP.
iPhone
iPhones have a hidden Field Test Mode: open the Phone app, dial *3001#12345#, and press call. Apple changes what it shows between iOS versions, so look for an entry labeled RSRP. iOS does not let apps read these values, so third-party iPhone apps cannot show them.
What the Numbers Mean
RSRP (Reference Signal Received Power) is signal strength for LTE and 5G. The closer to zero, the stronger: −85 dBm is stronger than −105 dBm.
| RSRP | Rating | What you notice |
|---|---|---|
| Better than −80 dBm | Strong | Full-speed data and reliable calls |
| −80 to −90 dBm | Good | Normal service |
| −90 to −100 dBm | Fair | Calls hold, data slows |
| −100 to −110 dBm | Poor | Dropped calls and failed messages |
| Below −110 dBm | No usable service | Below about −120 dBm the phone cannot hold a connection |
Strength is only half the story. RSRQ (signal quality) and SINR (signal versus interference and noise) show whether the signal arriving is clean enough to use:
| Metric | Good | Marginal | Problem |
|---|---|---|---|
| RSRQ | Above −10 dB | −10 to −15 dB | Below −15 dB |
| SINR | Above 13 dB (above 20 dB is excellent) | 0 to 13 dB | Below 0 dB: interference is stronger than the signal |
A strong RSRP with a poor SINR is the classic "full bars, nothing loads" problem: the phone hears several cells at similar strength and cannot separate the one it wants. More signal does not fix that; less interference does.
How to Take a Useful Reading
- Give it a few seconds. Readings move constantly. Hold the phone the way you normally would, wait, and note a typical value rather than a single snapshot.
- Compare the same way each time. Same phone, same carrier, and note whether it is on LTE or 5G, since the bands differ.
- Measure outside, then inside. The difference between the reading at the curb and the reading in a room is what your building costs you, and it tells you whether the problem is the network or the walls.
- Check every room that matters. Signal can change several dB from one side of a room to the other.
Skip the notebook. The free Cell Surveys app for iOS and Android logs readings with GPS as you walk and maps them as a coverage heatmap. On Android it works like a cell scanner, recording RSRP, RSRQ, and SINR with the serving cell's PCI and cell ID, plus the neighbor cells your phone can hear. iPhones do not let apps read measured signal levels.
What to Do With the Numbers
If the signal is fine outside but poor or unusable inside, the building is the problem, not the network. Our guide to why cell signal is bad inside your house walks through the fixes, cheapest first. If it is weak outside too, the fix is a different carrier or a booster's outdoor antenna in a better spot. For offices and larger buildings, see why signal drops indoors.
Keep Reading
Why Cell Signal Is Bad Inside Your House
Why your phone has signal outside but drops calls inside: the materials, 5G bands, and carrier factors behind weak home signal, and the fixes, cheapest first.
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What a DAS Signal Survey Measures
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Facilities Where This Comes Up
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Ready to Take Action?
Whether you need a professional signal survey or have questions about your facility's coverage, we're here to help.