Convert between RSSI dBm values and signal quality percentage for wireless links.
RSSI (Received Signal Strength Indicator) in dBm is commonly mapped to a 0-100% quality scale using a linear formula over the practical usable range of -100 dBm (unusable) to -50 dBm (excellent): quality% = 2 × (RSSI + 100). This mapping is a convention used by many WiFi drivers and utilities (not a physical law), chosen because -50 dBm and stronger is essentially always excellent, and -100 dBm is at or below the noise floor where a connection is effectively unusable.
RSSI to quality percentage
quality% = 2 × (RSSI + 100), valid for RSSI between -100 and -50 dBm
-50 dBm or stronger is treated as the ceiling for 'perfect' signal (100%) since further gains don't meaningfully improve connection quality, and -100 dBm is near or below the typical WiFi receiver noise floor, treated as the floor (0%, unusable).
No — it's a common convention (used in various OS and driver signal-quality displays) rather than a physical or IEEE standard. Different vendors sometimes use slightly different mapping curves or bounds for their quality bars.
Roughly -65 dBm or stronger (about 70%+ on this scale) is generally considered good for reliable, high-throughput WiFi. Below -80 dBm (about 40% or less), expect noticeably reduced speeds and possible drops.
RSSI measures absolute received signal power regardless of background noise. SNR measures how far that signal sits above the noise floor, which is actually the better predictor of usable throughput — a strong RSSI in a noisy environment can still perform poorly.