iPhone Field Test Mode (*3001#12345#*): How to Check Your Real Signal Strength

Signal bars are a guess. Two iPhones side by side can show different bars on the same mast, and carriers decide where the thresholds sit. Field Test mode is Apple's hidden screen that shows the real measurements behind the bars. It is the closest thing an iPhone has to a "network check code" or "test mode", and it is completely safe to open.

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How do I open Field Test mode?

1. Open the Phone app and go to Keypad.
2. Dial *3001#12345#*.
3. Press Call. Field Test opens instead of a call.

It works on any iPhone with a SIM or eSIM, on any carrier. It needs a cellular connection to show live readings, so Wi-Fi alone is not enough. The layout varies by iPhone model, modem and iOS version, but the readings below are on all recent models.

Where is the signal strength?

On recent iOS versions, Field Test opens on a dashboard. Tap the menu at the top and look for these sections:

• LTE > Serving Cell Meas for 4G. Look for rsrp0 (your main antenna), rsrq and sinr.
• NR or a 5G section when you are on 5G, with similar readings for the 5G cell.
• Serving Cell Info for the band and cell your iPhone is connected to.

What do RSRP, RSRQ and SINR mean?

Reading	What it measures	Good	Poor
RSRP	Signal strength from the mast	-80 dBm or higher	Below -110 dBm
RSRQ	Signal quality, including interference	-10 dB or higher	Below -15 dB
SINR	Signal compared with noise	13 dB or higher	Below 0 dB

The numbers are negative, so -75 is stronger than -95. Each 10 dB step is a big change: -90 dBm is ten times weaker than -80 dBm. A rough guide to RSRP:

• -80 dBm or above: excellent. Fast data and clear calls.
• -80 to -90 dBm: good.
• -90 to -100 dBm: fair. Data slows in busy areas.
• -100 to -110 dBm: poor. Calls may drop.
• Below -110 dBm: very weak. Expect "No Service" at times.

Strong RSRP with poor SINR means the signal reaches you but is noisy, often because of interference or a crowded cell. That is why full bars can still mean slow data.

How do I use Field Test to find better signal at home?

1. Open Field Test and go to the RSRP reading.
2. Stand still in each room for 15 to 20 seconds. The numbers update every few seconds.
3. Write down the RSRP for each spot, including near windows and upstairs.
4. Use the best spot for important calls, or place a router or signal booster there.
5. If every room is below -110 dBm, turn on Wi-Fi Calling in Settings > Apps > Phone.

Can I show dBm instead of bars?

Older versions of iOS had a trick to replace signal bars with the dBm number. It does not work on current iOS. Field Test is now the way to see the real number.

Is there an iPhone "test mode" like Android?

Not in the same way. Android has hidden test menus such as *#*#4636#*#*; iOS does not. Field Test is the only built-in dial code test screen. For hardware checks, Apple runs diagnostics through Apple Support, and apps like Secret Codes can test battery, display, touch, cameras, speakers and sensors. More on why Android codes do nothing on iPhone in Android secret codes on iPhone, and the full list of working codes in iPhone secret codes that work.

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