If you have a Mac laptop, this is the best.
The number you are looking for is the RSSI, which means Received Signal Strength Indicator. If you are on a computer running Mac OS X, you can also get the RSSI without installing any additional applications:
Press and hold the Alt key while clicking on the Wi-Fi icon on your status menu.
On the list of available networks, find the name of the network you are connected to, and the connection information including RSSI will be displayed immediately below.
Signal Strength Expected Quality
-30 dBm Maximum signal strength, you are probably standing right next to the access point.
-50 dBm Anything down to this level can be considered excellent signal strength.
-60 dBm Good, reliable signal strength.
-67 dBm Reliable signal strength.
-70 dBm Not a strong signal.
-80 dBm Unreliable signal strength, will not suffice for most services.
-90 dBm The chances of even connecting are very low at this level.
Wi-Fi Signal Strength: What Is a Good Signal And How Do You Measure It
https://www.metageek.com/training/resources/why-channels-1-6-11.html
https://www.metageek.com/training/resources/wifi-signal-strength-basics.html
https://www.howtogeek.com/426642/how-to-check-your-wi-fi-signal-strength/