Coaxial Cable Loss
Estimate the attenuation of a coaxial cable run (RG-58, RG-213, LMR-400, Heliax…) from the cable type, the frequency and the length. It interpolates the loss by √f from nominal factory data. Everything in your browser.
The loss at other frequencies
| Frequency | dB/100 m | Run |
|---|
The highlighted row is your frequency. The rest is interpolated the same way, by √f.
The same run on other cables
| Cable | dB/100 m | Run loss |
|---|
At your frequency and length. Handy to decide whether a better cable is worth it.
How it is calculated · √f and approximate values
1. Each cable comes with its nominal attenuation
in dB/100 m at a few reference frequencies (factory data).
2. Coaxial loss grows with the square root of
frequency (resistive loss): atten(f) ≈ atten(f₁)·√(f/f₁).
Between two references we interpolate linearly in √f.
3. Total loss:
dB = atten(f)/100 × length(m). This is the cable's own loss;
it excludes connectors and adapters (each adds ~0.1–0.5 dB).
4. Every 3 dB is half
the power; 10 dB leaves 1/10.
The values are approximate: they vary by manufacturer,
temperature and cable quality.
Runs locally in your browser · no sign-up · nothing leaves your browser.
How it works
The calculator estimates the attenuation of a coaxial cable run from three inputs: cable type (RG-58, RG-6, RG-213, LMR-400, LMR-600 or Heliax 1/2"), frequency in MHz and length in meters. Each cable carries its nominal factory attenuation in dB/100 m at several reference frequencies, and the total run loss is dB = atten(f)/100 × length. It also shows the percentage of power that survives: 10^(−dB/10) × 100.
Between reference frequencies the value is interpolated in √f, because the resistive loss of coax (skin effect in the conductor) grows roughly with the square root of frequency: atten(f) ≈ atten(f₁) × √(f/f₁). Outside the data range the tool extrapolates with the same law and flags it. Values are approximate: they vary with manufacturer, temperature and cable condition, and do not include connectors or adapters (add about 0.1 to 0.5 dB each).
Example: 30 m of LMR-400 for 2.4 GHz WiFi
- At 2400 MHz, LMR-400 attenuates 12.7 dB/100 m (nominal factory figure).
- Run loss:
12.7 / 100 × 30 = 3.81 dB. - Power reaching the far end:
10^(−3.81/10) ≈ 41.6 %: more than half is lost in the cable. - The comparison table shows the same run in RG-58 would lose over 15 dB: unusable at that frequency.