RSSI
Received Signal Strength Indicator
The number behind the Wi-Fi bars on your screen. RSSI measures how strong a signal a device is actually receiving — and reading it in dBm tells you far more than four little bars ever could.
RSSI — Received Signal Strength Indicator — is a measurement of how much signal power a device is picking up from an access point. It is the real number underneath the Wi-Fi signal bars in your status bar. Where bars are a rough four- or five-step approximation, RSSI gives you a precise figure, almost always reported in dBm, that you can use to judge coverage and compare locations.
Reading the numbers
RSSI in dBm is a negative scale, and closer to zero means stronger. Here is how the values translate to real experience:
| RSSI | Quality | What to expect |
|---|---|---|
| -30 to -50 dBm | Excellent | Maximum speeds; you are right by the access point |
| -50 to -60 dBm | Very good | Fast and reliable for everything |
| -60 to -67 dBm | Good | Reliable video calls and streaming |
| -67 to -70 dBm | Marginal | Usable but speeds begin to drop |
| -70 to -80 dBm | Weak | Slow, unstable; dropouts likely |
| Below -80 dBm | Very poor | Often unusable |
A practical target is to keep important devices at -67 dBm or better; that is the threshold below which latency-sensitive apps start to suffer.
Why it is negative
RSSI is expressed in dBm, a logarithmic unit relative to one milliwatt of power. Wi-Fi signals carry only tiny fractions of a milliwatt by the time they reach your device, so on the dBm scale they come out as negative numbers. This trips people up constantly: -50 is a stronger signal than -70, even though 70 is a bigger number, because both are below zero. If the idea of a negative power scale is unfamiliar, the dBm entry explains it in full.
Why signal strength alone is not the whole story
A strong RSSI is necessary for good Wi-Fi, but it is not sufficient. The airwaves also contain noise and interference from neighbouring networks, microwaves, and other devices. What ultimately determines your usable speed is how far your signal stands above that noise — the signal-to-noise ratio. A device can show a healthy -55 dBm RSSI yet still struggle if the noise floor is high. This is why two spots with the same RSSI can perform differently, and why serious Wi-Fi tuning looks at both numbers together.
How to read your RSSI
Most platforms can show the actual value rather than just bars. On a Mac, hold Option and click the Wi-Fi icon to see RSSI in dBm. On Windows, netsh wlan show interfaces reports signal as a percentage that maps to RSSI. On Android and iOS, free Wi-Fi analyser apps display per-network RSSI and let you walk around to map coverage. Watching the number change as you move is the fastest way to find dead zones and decide where an access point would help.