What it means
RSSI is the strength of a Bluetooth signal as your phone receives it, reported in dBm and always negative. Closer to zero means stronger, which usually means closer.
Around −30 dBm is touching distance. −60 is roughly the same room. −80 and below is far away or through a wall.
It measures received power, not distance. Distance is inferred from it, and the inference is rough because walls, metal, water and human bodies all absorb 2.4 GHz radio.
The practical consequence is that you should read the trend rather than the value. A number that climbs as you walk is reliable information. A single reading is not.
Related terms
The other pieces of Bluetooth vocabulary that change how you search.
- BLE: Bluetooth Low Energy
- Advertising interval: How often a device broadcasts
- MAC randomisation: Rotating Bluetooth identifiers
- Bluetooth Classic: The older streaming mode
- Coin cell: The battery in most tags
- Clap to find your phone, Clap tab
- How to find something you lost in an airport
- Full glossary, the complete list
Common questions
Can RSSI give an exact distance?
No. Transmit power varies by device and the environment distorts the reading heavily. Direction of change is trustworthy; a precise metre figure is not.
Why does RSSI jump around when I stand still?
Radio at 2.4 GHz reflects off metal and is absorbed by water, and a human body is mostly water. Turning around can move the reading by 10 dBm.
In the app: The scan shows this value live for every device around you. Read about Bluetooth Scanner.