WiFi Calc is a link budget calculator. It will enable you to determine the correct antenna gain, radio power and distance for a point-to-point wireless link.

Usage is straight forward. Just input the antenna gain, radio power in dB and distance in kms. and it will compute the signal for each end of the link.

The required signal on each end of the link depends on the receive sensitivity (for a required link speed) of the radio equipment you are using. This information can be found on your radio equipment's datasheet.