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Your iPhone’s signal bars are only a rough visual estimate. Field Test mode exposes the radio measurements behind them, including values such as RSRP, RSRQ, SINR, network type, band, and serving-cell information when your iPhone and carrier make those details available.
The interface differs by iPhone model, iOS version, carrier, SIM or eSIM setup, and whether the phone is connected to LTE, 5G NSA, or 5G SA. Do not expect every iPhone to show the same menu or every metric.
Open Field Test mode on an iPhone
- Open the Phone app.
- Tap Keypad.
- Enter
*3001#12345#*exactly. The code must include both asterisks and both hash characters. - Tap the green Call or Dial button. The label varies by iOS version and locale.
This does not place a normal, billable telephone call. It opens Apple’s built-in cellular diagnostic interface.
On recent iOS releases, the screen may be titled Field Test. It can initially look blank while the modem supplies data, so wait several seconds before assuming that it failed.
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Where to find the signal reading
There is no single menu path that works on every iPhone. Depending on the installation, Field Test may open to a dashboard showing carrier and radio information, an All Metrics view, or carrier-specific sections.
Look for headings or entries containing terms such as:
- LTE, Serving Cell, or Cell Info
- 5G NR or NrServingCellInfo
- RSRP, RSRQ, or SINR
- Band, Network Type, or Connection Type
- Cell ID, CI, NCI, TAC, PLMN, MCC, or MNC
If your screen has a search field or an All Metrics option, use it to search for RSRP. On another iPhone, the same information may be grouped under a serving-cell page instead.
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How to read the real signal-strength number
For LTE and 5G radio measurements, the most useful received-power value is usually RSRP—Reference Signal Received Power. It is shown in dBm, typically as a negative number.
With dBm, a number closer to zero is stronger. For example, -80 dBm is stronger than -110 dBm.
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| RSRP | General interpretation |
|---|---|
| -80 dBm or better | Strong reception in many situations |
| -81 to -95 dBm | Good or usable reception |
| -96 to -105 dBm | Moderate; performance may vary indoors or under load |
| -106 to -115 dBm | Weak; slower data and dropped connections become more likely |
| Below -115 dBm | Very weak; the phone may struggle to maintain service |
These ranges are practical guidelines, not guarantees. A strong RSRP reading does not ensure fast internet if the cell is congested, the backhaul is limited, or interference is high.
RSRQ and SINR: why power is not the whole story
RSRP tells you how much reference-signal power the phone receives. It does not describe the cleanliness or usable capacity of that signal.
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- RSRQ indicates signal quality. It is affected by interference and network load; values closer to zero are generally preferable.
- SINR measures signal relative to interference and noise. A higher positive value is generally better.
Field Test does not expose these values consistently. Their meaning and reliability can also vary between LTE and 5G modes. If an iPhone shows only RSRP, that is not evidence that the phone is defective.
Check LTE and 5G details
When available, the diagnostic screen may show the serving band and identifiers for the cell to which the phone is connected. LTE pages may include cell_id or ci, TAC, PLMN, MCC, and MNC. 5G pages may use NCI or cell_id.
A 5G icon alone does not prove that the phone is using standalone 5G. In 5G NSA (non-standalone), 5G is anchored to an LTE connection. 5G SA (standalone) connects to a 5G core network without that LTE anchor. Field Test may identify the mode, but the relevant label is not available on every carrier configuration.
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Get a meaningful measurement
- Turn off Wi-Fi temporarily from Settings → Wi-Fi, or use Control Center to disconnect from the current Wi-Fi network.
- Open Field Test mode and note the RSRP, RSRQ, and SINR values that are available.
- Wait for the numbers to settle. Radio values change as the modem updates its measurement.
- Repeat the test in the places where service matters: beside a window, at your desk, in a particular room, or outdoors.
- Take several readings rather than treating one number as a permanent coverage rating.
Turning off Wi-Fi is not required to open Field Test mode. It prevents a Wi-Fi connection from masking poor cellular data performance while you test.
Why Field Test may show less information than expected
Field Test is not a universal diagnostic dashboard. Apple, the modem firmware, and the carrier profile determine which fields are exposed. A recent iPhone may show carrier information, network type, band, signal strength, and tower identifiers while omitting RSRQ, SINR, or detailed cell menus.
The following common assumptions are unreliable:
- “Cell Info is always present.” It is not. The section may be renamed, reorganized, or absent.
- “RSRP is always available.” Some carrier and radio configurations do not expose it in the visible interface.
- “Every iPhone has the same Field Test menus.” Menus vary by iOS release, iPhone model, modem, carrier, SIM or eSIM, and current connection.
- “The 5G icon proves standalone 5G.” The phone may be using 5G NSA.
Field Test troubleshooting
The code does nothing
Make sure you entered *3001#12345#* in the Phone app’s keypad, not in a web search or a text message. Include the leading and trailing asterisks. If the code still fails, restart the iPhone, confirm that cellular service is active, and try again. Carrier or software differences can affect access.
The Field Test page is blank
Wait briefly for the metrics to populate. Move to an area with cellular coverage and make sure Airplane Mode is off. If it remains blank, restart the phone and retry with Wi-Fi disconnected. A blank or reduced screen can also reflect what the carrier and current radio mode permit the interface to display.
The values keep changing
That is normal. These are live measurements, not a permanent score. Values change when you move, the phone changes bands or serving cells, or the network switches between LTE and 5G. For comparisons, hold the phone in the same position and test at the same location for several seconds.
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The signal bars look good but data is slow
Compare RSRQ and SINR if they are available, then test again with Wi-Fi off. Strong received power can coexist with interference, congestion, or a poor network connection. Field Test measures the radio link; it does not measure every part of an internet connection.
Exit Field Test mode
Use the normal app switcher to close the Field Test screen, or tap another app. If the interface leaves you in an unusual state, lock and unlock the iPhone or restart it. Opening Field Test does not permanently change your cellular settings.
Older guides often describe converting the status-bar signal bars into a persistent dBm display. That was an older iOS behavior and is not the current Field Test workflow. Use the diagnostic screen instead of relying on those instructions.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.FAQ
Does iPhone Field Test mode cost money?
No. Entering *3001#12345#* opens Apple’s diagnostic interface; it does not place an ordinary billable phone call.
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What is the best iPhone signal-strength value to check?
RSRP is usually the main received-power measurement for LTE and 5G. Because it is negative, -85 dBm is stronger than -105 dBm. Check RSRQ and SINR too when available because power alone does not describe interference or congestion.
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Why can’t I find RSRP or Cell Info?
The available fields depend on the iPhone, iOS release, modem, carrier profile, SIM or eSIM configuration, and current LTE or 5G connection. Missing fields do not necessarily indicate a hardware problem.
Was Field Test mode removed from iOS 16?
There is no reliable basis for saying it was universally removed. The dialer code continues to be reported as working on newer releases, although the interface and the amount of information shown have changed.
Should I turn off Wi-Fi before using Field Test mode?
It is not required to enter the mode, but it is recommended when testing cellular performance. Otherwise, Wi-Fi may provide the data connection and make poor cellular service harder to identify.
The Bottom Line
Open Phone → Keypad, enter *3001#12345#*, and tap Call or Dial. Find RSRP if your iPhone exposes it, remembering that a value closer to zero is stronger. Treat Field Test readings as live, location-specific radio measurements—not as a permanent coverage grade—and expect the available menus to vary.
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