Coaxial Cable Loss

Enter frequency and length to estimate attenuation (dB), power delivered, and voltage ratio. Choose a coax type or enter a custom loss spec.

How to Use

  1. Select a coax type (or choose Custom).
  2. Enter the frequency and cable length.
  3. (Optional) Enter input power or input voltage to estimate delivered values.
  4. Open “Show Work” to see the math and conversions.
Signal Path View
Attenuation (dB) → power and voltage ratios.
Loss
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Power Delivered
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V Ratio
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dB / 100
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Link Quality: —
Input —
TX / Source Coax — RX / Load Heat overlay scales with total loss. “Power Delivered” is the fraction that reaches the load.
Inputs & Settings
Pick coax type or Custom loss spec. Tool computes attenuation and ratios instantly.
Note: “generic” values are approximate. Use Custom if you have datasheet loss (dB per 100 ft/m).
Examples: 27 MHz (CB), 146 MHz (VHF), 450 MHz (UHF), 2.4 GHz (Wi-Fi)
Straight run length (does not include extra inside connectors/loops).
Use the datasheet value at your frequency. If using a chart, choose the closest frequency point.
If provided, tool estimates delivered power after coax loss.
If provided, tool estimates delivered voltage using voltage ratio.
Show Work (step-by-step)
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Work uses standard dB relationships: power ratio uses 10^(−dB/10); voltage ratio uses 10^(−dB/20).

Reference

  • Total loss (dB): Loss_dB = (LossSpec_dB_per_100 × (Length / 100))
  • Power ratio: Pout/Pin = 10^(−Loss_dB/10)
  • Voltage ratio: Vout/Vin = 10^(−Loss_dB/20)
  • Delivered power: Pout = Pin × (Pout/Pin)
  • Delivered voltage: Vout = Vin × (Vout/Vin)

This tool estimates attenuation only. It does not model mismatch, SWR, connectors, or bends unless you incorporate them into your loss spec.

FAQ

Is dB loss linear with length?

Yes—attenuation in dB adds linearly with length when using a dB-per-distance spec.

Why does voltage ratio use 20 and power ratio uses 10?

Because power is proportional to voltage squared (for matched impedance), so voltage uses 20·log10 and power uses 10·log10.

What about connectors/adapters?

Add their insertion loss (in dB) to the total loss, or bake it into your Custom loss value.

Does thicker coax always win?

Generally thicker, lower-loss coax helps more at higher frequencies and long runs, but flexibility, cost, and connector type also matter.

Tool Info

Last updated:

Updates may include additional coax presets, improved unit handling, and edge-case validation.