Amateur Radio Calculators

Free amateur radio (HAM) calculators.
Antenna length, path loss, SWR, repeater coverage, and more.

Convert between dBm and watts for amateur radio power levels. Includes common reference points and transmitter power chart.

Calculate the optimal length for a half-wave dipole antenna. Enter frequency to get total length and each leg length in feet and meters.

Calculate free-space path loss (FSPL) between two radio stations. Enter frequency and distance to get signal attenuation in dB.

Estimate the radio horizon and coverage radius of a ham radio repeater based on antenna height. Uses line-of-sight radio propagation formula.

Calculate Standing Wave Ratio (SWR) from impedance mismatch, and find the percentage of power reflected back. Essential for antenna tuning.

Convert between radio frequency and wavelength. Calculate quarter-wave and half-wave antenna dimensions for any amateur radio band.