Wi-Fi Heatmap Planner › Guides
Wi-Fi signal strength (RSSI) explained: what dBm is good?
Last updated: October 3, 2026.
RSSI is the received signal strength, measured in dBm. The numbers are negative, and the closer to zero, the stronger the signal. Each 3 dB drop roughly halves the power.
What the numbers mean
| RSSI | Typical meaning |
|---|---|
| -50 dBm or stronger | Excellent, usually close to the access point |
| -50 to -60 dBm | Very good |
| -60 to -67 dBm | Good; common target for voice and video |
| -67 to -70 dBm | Fair; basic coverage |
| -70 to -80 dBm | Weak; slow or unreliable |
| Below -80 dBm | Usually unusable |
These are general guides. Requirements vary with devices, applications and interference.
How walls reduce signal
Typical planning values for one wall are about 2 dB for glass, 3 dB for drywall, 6 dB for brick, 10 dB for concrete and 18 dB or more for lift or service cores. Higher bands such as 5 GHz and 6 GHz usually lose more. Real values vary, so measure on site where it matters.
Reading a heatmap
A heatmap colours each point by its strongest predicted signal. Use the legend to find your target level, and look at the outline that marks where the minimum RSSI is met. A secondary layer shows the second-strongest access point, which helps check roaming coverage.
Try it on your own floor plan with the free Signal Plan Wi-Fi heatmap planner.