WiFi Signal Strength Explained: dBm, Bars and What Is Good
WiFi signal strength is measured in dBm (decibels relative to one milliwatt). The numbers are negative, and closer to zero means stronger. Here is how to read them.
WiFi signal strength chart
| Signal (dBm) | Quality | Good for |
|---|---|---|
| -30 to -50 | Excellent | Everything, at full speed |
| -50 to -60 | Very good | 4K streaming, gaming, video calls |
| -60 to -67 | Good | HD streaming and calls |
| -67 to -70 | Fair | Browsing, email, SD video |
| -70 to -80 | Weak | Basic browsing, frequent drops |
| Below -80 | Unusable | Disconnects |
Why a few dBm matter so much
dBm is logarithmic. Every 3 dBm drop halves the received power, and every 10 dBm is a tenfold drop. Going from -60 to -70 dBm means the signal is ten times weaker, which is why one extra wall can turn a good room into a dead zone.
How bars map to dBm
Each manufacturer uses its own scale, but a common mapping is: four bars at -55 dBm or better, three bars from -55 to -66, two bars from -67 to -77, one bar below that.
Strength is not the same as quality
A strong signal on a crowded channel can still perform badly. That is why our tools measure quality directly: latency, jitter, packet loss and speed. Try the walk test to see how quality changes from room to room.
Is -70 dBm good for WiFi?
It is on the weak side. Browsing works, but streaming and video calls may stutter. Aim for -67 dBm or better where you use WiFi most.
Is -40 dBm good?
Yes, that is excellent. You are likely close to the router.