Skip to content

Coax Loss Calculator

Calculate coaxial cable RF signal loss in dB from cable type, run length, and frequency. Estimate transmit power delivered to your antenna.

Use this result well

Inputs that matter
Cable Type, Cable Length, Frequency
Output to expect
Coax Cable Loss Calculator
  • Check the units and required inputs before comparing results.
  • Keep the assumptions with a copied result so you can reproduce the calculation later.
Was this tool helpful?

Related Tools

Tools you might need next

SWR Calculator

Calculate Standing Wave Ratio from forward and reflected power readings. Convert SWR to return loss and reflected power percentage.

Recommended next stepHam Radio
RF Power Calculator

Convert RF power between watts, dBm, and dBW. Calculate power density and link budget components for ham radio and wireless.

Recommended next stepHam Radio
Antenna Length Calculator

Calculate half-wave dipole and quarter-wave vertical antenna element length from frequency. Includes velocity factor correction for wire type.

Recommended next stepHam Radio

Reference & details

How it works

Total Loss

Cable loss specifications are given per 100 feet at specific frequencies. Scale linearly with length. Loss increases with frequency.

Loss (dB) = Loss per 100 ft (dB) × (Length ÷ 100)

Power at Antenna

Convert dB loss to power ratio. 3 dB loss = half power at antenna. 1 dB loss ≈ 79% power delivered.

P_antenna = P_transmitter × 10^(−Loss/10)

Receive Loss Symmetry

Feed line loss affects both transmit and receive equally. 3 dB coax loss costs one S-unit on receive sensitivity.

Receive degradation = Same dB loss as transmit

Updated: July 2026

Example Scenarios

RG-58 loss ~1.5 dB/100ft at 14 MHz → 1.5 dB total. 100W transmitter delivers ~71W to antenna.

50 ft LMR-400 at 146 MHz: 0.9 dB loss vs 3.5 dB for RG-58 — significant improvement for weak signal work.

200 ft LMR-600 at 50 MHz: 1.8 dB loss. Compare against hardline options for permanent installations over 150 ft.

FAQ

LMR-600 and hardline (Heliax) have lowest loss for amateur use. LMR-400 is the sweet spot for most HF/VHF installations. RG-58 is convenient but lossy above 30 MHz.

Yes. Loss is proportional to √frequency approximately. RG-58 acceptable at HF (1–2 dB/100ft) but poor at UHF (6+ dB/100ft).

Keep total loss under 3 dB (half power) when possible. At HF, 100–200 ft of LMR-400 is fine. At UHF, minimize length and use low-loss cable.

Yes. High SWR increases current in feed line, increasing I²R losses. Low-loss cable plus good antenna match maximizes power delivery.

RG-8X is thinner and easier to route but has roughly 2× the loss of LMR-400. Use LMR-400 for runs over 50 ft or frequencies above 50 MHz.

About Coax Loss Calculator

Coaxial cable attenuates RF power between transceiver and antenna. Enter cable type, run length, and operating frequency to calculate total loss in dB and percentage of power reaching the antenna.