Calculating the effective radiated power for a ham radio station can be difficult. This app can help! Enter a few pieces of information regarding your station setup and Ham Radio Tools can tell you your ERP and let you know if you are required by the FCC to do an RF evaluation.
Ham Radio Tools also includes calculators for antenna length, Ohm's law, resonant frequency, grid square, and a list of common Q codes. The grid square calculator can convert an entered lat/long to grid square, or can use your GPS to find your current location and grid square.