You may want to have a look at this Excel file if you're into experimenting with WiFi networks. All honors go to Onno W. Purbo YC0MLC ex YC1DAV for making this nifty thing.
A simple model for 2.4GHz propagation in a building
Transmission power(TX) : 10 dB
Receiver sensitivity(RX) : -90 dB
Power budget = TX - RX = 10 --90 = 100 dB
Minus 70 dB for first 10 meter of range leaves 30 dB
Double the rane for every 10 dB
Range 20 m leaves 20 dB
Range 40 m leaves 10 dB
Range 80 m leaves 0 dB
I wasn't aware that Excel-files are banned on this forum. So, of course the file can be zipped and re-upped which has been done now for all to enjoy. It's really a very good file for all who do WiFi work.
Thanx to klystron for the quick & dirty 1-2-3 rule-of-thumb formula for calculating range. I wonder if one is better than the other