This app was mentioned in 6 comments, with an average of 2.17 upvotes
So that's more like a theoretical coverage map, right? It's not based on an actual signal measurements. I would do some measurements ( https://play.google.com/store/apps/details?id=com.manageengine.wifimonitor) and compare the two maps.
I don't know that I love its output, but I used the Wifi Analyzer and Surveyer to generate these maps the other day. It's free, and simple.
One thing that is really nice about this app over others I tried is that when pulling each sample, it samples every access point it can see. So you only need to do one lap of your house, and it'll tell you the signal strength from all the access points.
https://play.google.com/store/apps/details?id=com.manageengine.wifimonitor&hl=en_US
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I am sure there are better ones but it gets the job done for Free99!
If you don't mind using Android instead, this app works very well for mapping. https://play.google.com/store/apps/details?id=com.manageengine.wifimonitor
i used WIFI Analyzer and Surveyor app on android, it is free
https://play.google.com/store/apps/details?id=com.manageengine.wifimonitor&hl=en