Coaxial Cable Loss Calculator

Calculate transmission loss for common coaxial cables with frequency interpolation.

What is coax cable loss?

Coax cable is like a water pipe for RF signals — every pipe leaks a little. Longer and thinner pipes leak more. The signal that leaves your transmitter is always stronger than what arrives at the other end, and this calculator tells you exactly how much is lost.

Why it matters: 100 feet of cheap RG-58 cable to your TV antenna can lose half the signal. Choosing the right cable type and length makes the difference between a clear picture and static.

Parameters
Select cable type, run length, and frequency.

Total run from transmitter/receiver to antenna or device.

Higher frequencies lose more signal over the same length of cable.

0 dBm = 1 mW, 30 dBm = 1 W, 43 dBm = 20 W

LMR-400

Popular trunk cable. Low loss, semi-flexible.

50 ΩVF 0.85
Cable Loss Results
LMR-400 · 100 ft · 144 MHz
Total Cable Loss1.68 dB
Atten. rate at freq.1.68 dB / 100 ft
Atten. rate0.513 dB / m
Power In30 dBm (1.000 W)
Power Out28.32 dBm (678.555 mW)
Power Lost321.445 mW
Power Through67.9 %
Power Lost (%)32.1 %
Length (ft)100.00 ft
Length (m)30.48 m
Electrical Length76.4°

Loss values from manufacturer datasheets. Interpolation uses √f scaling (skin-effect dominated loss). Actual loss may vary with temperature, connector quality, and cable age. Connector losses typically add 0.1–0.5 dB per connector.