RFLinkCalc is a numerical calculation tool for radio engineers. It models the characteristics of an RF link, including Wireless Internet (WiFi) links. You can compute the maximum distance, required transmitter power level, or gain margin.

You enter in all of the following values (except what you are trying to calculate) and RFLinkCalc does the rest!

Frequency in MHz
Transmitter Power in dBm
Transmitter Antenna Gain in dBi
Transmitter Cable Loss in dB
Distance in miles or kilometers
Receiver Sensitivity in dBm
Receiver Antenna Gain in dBi
Receiver Cable Loss in dB
Gain Margin in dB

The Free Space Loss and Received Signal values are also calculated.

The EIRP/ERP Calculator computes the EIRP (Effective Isotropic Radiated Power) and ERP (Effective Radiated Power) in both watts and dBm from the transmitter power and antenna gain. The field strength in dBuV/m is also computed for distances of 3 and 10 meters.

The Field Strength Calculator converts between the following units:
V/m (volts per meter)
dBuV/m (dB relative to one microvolt per meter)
dBuA/m (dB relative to one microamo per meter)
pT (pico Tesla)
dBpT (dB relative to one pico tesla)
Tesla
Gauss
A/m (amperes per meter)
mW/cm² (milliwatts per square centimeter)
W/m² (watts per square meter)