What does Wi-Fi signal strength in dBm mean?
dBm is the power of the signal that reaches your device, compared with 1 milliwatt. For Wi-Fi the value is always negative, and the closer to zero, the better: −60 dBm or better is excellent, −60 to −67 dBm is good, and below −80 dBm the connection drops often.
Aim for −67 dBm or better in the rooms you use. That is the level where HD video and video calls run without freezing.
Small differences in the number are big in power: −67 dBm carries 20 times more power than −80 dBm.
What is a good Wi-Fi signal in dBm?
| Signal | Level | In practice |
|---|---|---|
| −60 dBm or better | Excellent | 4K streaming, online gaming and the full speed of your plan. |
| −60 to −67 dBm | Good | Stable HD video and video calls. The target for rooms you use. |
| −67 to −72 dBm | Fair | Browsing and messaging work; video may stutter. |
| −72 to −80 dBm | Weak | Slow and unstable. |
| below −80 dBm | No usable signal | The connection drops often. |
These are the ranges the planner uses to color the map. They apply to the signal a device receives; for the link between two mesh nodes the target is different: −70 dBm or better.
Why is the number negative?
Because 0 dBm is 1 milliwatt, and the signal that reaches your phone is a tiny fraction of that. A mesh node transmits at around 23 dBm, about 200 mW. After a few meters and walls, something like −60 dBm reaches your device: one millionth of a milliwatt.
The scale moves in steps of 10: −30 dBm is one thousandth of a milliwatt, −40 dBm is ten times less than that, and so on. Every 3 dB lower is half the power.
dBm, bars or percentage: which one counts?
dBm does. Your phone’s bars and the percentage in Windows are conversions each maker does its own way: three bars on one device can be two on another, with the same signal. dBm is the real measure, and it is what Wi-Fi analyzer apps show as RSSI.
How do I measure signal strength in dBm?
- Android: install a Wi-Fi analyzer app; it shows the dBm of your network and the neighbors’.
- iPhone: iOS does not show dBm in Settings. Install Apple’s AirPort Utility, turn on “Wi-Fi Scanner” under Settings › AirPort Utility and run a scan.
- Mac: hold the Option key and click the Wi-Fi icon; the value shows as RSSI.
- Windows: the system shows a percentage, not dBm. A Wi-Fi analyzer app shows the value in dBm.
Measure standing still, with the device in your hand, where you usually use it, and repeat a few times: the value moves a few dB from one second to the next.
Does a strong signal guarantee fast internet?
No. dBm tells you how much signal arrives, not how much noise comes with it. In a building with dozens of networks on the same channel, a −67 dBm signal can deliver less than a −72 dBm signal in a detached house. Speed also depends on your plan, your device and the channel width. Good signal is a requirement for fast internet, but not enough on its own.
Why does my phone show signal but the connection fails?
Because Wi-Fi is a two-way street. Your phone transmits with much less power than the router, so at the edge of coverage it still hears the router, but the router no longer hears it well. The signal looks fine and pages do not load. That is why it pays to aim for −67 dBm or better, not for the last spot where the phone still shows the network.
The numbers in this guide come from the model the planner uses (distance loss with exponent 2.5 plus the loss of each wall) and have a typical error of ±8 dB. Use them to compare options, then confirm with a measurement once everything is set up.
Frequently asked questions
Is −50 dBm better than −70 dBm?
Yes. The closer to zero, the stronger: −50 dBm carries a hundred times more power than −70 dBm.
What signal do I need for online gaming?
Aim for −60 dBm or better. Games depend more on stability and latency than on speed, and a strong signal reduces the retransmissions that cause lag spikes. For a console or desktop computer, a network cable is better still.
What is RSSI?
It stands for received signal strength indicator. In analyzer apps and on the Mac, RSSI is shown in dBm and is the same number as on this page.
Support the project
Planejador WiFi is free and open source. If it helped you pick the right router, you can send any amount of bitcoin over the Lightning Network with this BOLT 12 offer:
lno1pgv9qmrpdejk5ctydaezq4mfge5jqer0deshg6t0dcfpyurvv9hx26npv3hhyamfve5jucm0d5tzzq4uh5utfj7c2zmlwdeftewjv44sfdthp73slzgzv3hsnswea4ed65
Scan the QR code or paste the offer into a wallet that supports BOLT 12, such as Phoenix and Zeus.