Coax Cable Loss Calculator
Attenuation of RG-58, RG-213, LMR-240/400/600 and more at any frequency and length — with the power actually reaching your antenna.
At UHF and up, fat cable beats more transmit power: 20 m of RG-58 at 435 MHz eats ~6.7 dB — more than three-quarters of your power as heat. Loss also applies on RECEIVE, directly degrading SNR before the radio. Above ~3 dB run-loss, move the radio closer, use LMR-400-class cable, or put the amplifier/LNA at the antenna.
Coax Loss Calculator computes cable attenuation for common coax types at your frequency and length — free, instant and private in your browser. Ham and scanner users, WiFi long-shot builders and anyone choosing between cable grades use it to skip the datasheet algebra: type your numbers, read the answer with the substituted formula shown step by step, and share an exact permalink of the calculation.
About Coax Cable Loss Calculator
Coax Loss Calculator computes cable attenuation for common coax types at your frequency and length using the standard engineering relation: loss = k(100 MHz)·√(f/100)·L/100 — skin effect makes attenuation grow with √f. Worked live: 20 m of RG-58 at 435 MHz eats 6.7 dB — over three-quarters of your power becomes heat. The result recalculates on every keystroke, the worked-example panel shows your numbers substituted into the formula, and the Copy permalink button encodes the inputs in the URL so a colleague opens exactly your calculation. Everything runs client-side — nothing you type leaves your device.
How to use Coax Cable Loss Calculator
- 1Enter your values — the tool starts with realistic defaults for this exact use case, so the worked example is meaningful immediately.
- 2Read the live result and the worked-example panel, which substitutes your numbers into the formula step by step.
- 3Adjust any input to compare scenarios, then use Copy result or Copy permalink to share the calculation.
Why use Coax Cable Loss Calculator?
- ✓Implements the real formula — loss = k(100 MHz)·√(f/100)·L/100 — skin effect makes attenuation grow with √f — with the substitution shown, not a black box
- ✓Built for ham and scanner users, WiFi long-shot builders and anyone choosing between cable grades
- ✓Copy result and permalink buttons — share the exact calculation in a README, forum answer or design review
- ✓100% free, no sign-up, runs entirely in your browser (works offline once loaded)
Frequently asked questions
How do you calculate coax loss?+
Cable attenuation for common coax types at your frequency and length follows loss = k(100 MHz)·√(f/100)·L/100 — skin effect makes attenuation grow with √f. For example, 20 m of RG-58 at 435 MHz eats 6.7 dB — over three-quarters of your power becomes heat. The calculator applies the same relation and shows the substituted arithmetic so you can verify every step.
Does coax loss matter on receive too?+
Equally — every dB of cable loss directly degrades received SNR before the radio can help. For weak-signal work the classic fix is moving the first amplifier (LNA) to the antenna so the cable carries an already-boosted signal.
When is fat expensive coax worth it?+
Above ~3 dB of run loss, or any UHF+ run beyond ~10 m. LMR-400 versus RG-58 on a 20 m, 435 MHz run saves ~5 dB — more than tripling effective radiated power, cheaper than any amplifier delivering the same.
Is the Coax Loss Calculator free and private?+
Yes — completely free with no sign-up or usage limits, and it runs entirely in your browser: the values you enter are never uploaded or stored on a server.
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