Coax Cable Loss Calculator: RF Loss & Power at Antenna

How much RF power are you losing in your coax? Our Coax Cable Loss Calculator estimates signal loss based on cable type, frequency, and cable length, then calculates how much transmitter power remains at the antenna.

Select your coax, enter the operating frequency and cable length, and you’ll see the estimated attenuation in dB, total cable loss, power reaching the antenna, and percentage of power lost.

Coax Cable Loss Calculator

Estimate RF signal loss through coaxial cable based on cable type, frequency, and cable length. Enter transmitter power to also see the approximate power remaining at the antenna.

Coax cable

Frequency (MHz)

Cable length

Length unit

Transmitter power (watts)

Results

Cable attenuation—

dB per 100 ft

Total cable loss—

for your cable length

Power reaching antenna—

assuming a matched system

Power lost in cable—

—

How to interpret the result

Cable loss is expressed in decibels. Longer cable runs produce more loss, and attenuation generally increases with frequency. The calculator uses manufacturer-published attenuation data for the listed cable examples and log-interpolates between published frequency points where necessary. Results are estimates; actual loss can vary with cable construction, connectors, temperature, frequency, and installation.

Important note about transmitter power

The calculated output power is the theoretical power remaining after the stated cable attenuation. It is not a cable power-rating check. Maximum safe transmitter power depends on the specific cable, frequency, installation conditions, connector losses, VSWR, temperature, and manufacturer specifications.

Preset attenuation data is based on manufacturer specifications for Belden 8219 (RG-58), Belden 8214 (RG-8), Belden 8267 (RG-213), Belden 9913, and Times Microwave LMR-400. Check the exact cable manufacturer’s datasheet for final design work.

You may also be interested in this tool:

Calculate Your Antenna Length

Not sure how long your antenna should be?
Our Antenna Calculator calculates wavelength and practical starting dimensions for quarter-wave, half-wave, dipole, and 5/8-wave antennas.

👉 Calculate Your Antenna Length →