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Attenuation Over Distance Calculator

Work out attenuation over distance instantly with clear inputs, formula shown and shareable results.

About Attenuation Over Distance Calculator

Copper attenuation rises with the square root of frequency, which is why a Cat 6 run that loses 1.8 dB per 100 m at 100 MHz loses nearly 2.8 dB at 250 MHz — and why higher-speed standards impose shorter distance limits on the same cable. Fibre attenuation is essentially flat with modulation rate, which is what makes it the choice for long runs.

Formula

Attenuation

cable loss = (distance / 100) x loss per 100 m x sqrt(frequency / 100) for copper; total = cable loss + connector loss; power retained = 10^(-loss/10)

Worked example

With the default values below, Attenuation Over Distance Calculator returns Total attenuation of 3.36. Change any input above and every figure here is recalculated in your browser.

Inputs used

Distanceminimum 0.01 m
90 m
Mediumone of Cat 5e copper (~2.0 dB/100m at 100 MHz), Cat 6 copper (~1.8 dB/100m), Coaxial RG6 (~6.8 dB/100m at 1 GHz), OM4 multimode fibre (3.0 dB/km)
Cat 6 copper (~1.8 dB/100m)
Signal frequencyminimum 1 MHz
250 MHz
Connector and termination lossaccepts 0–20 dB
0.8 dB

Results

Total attenuation
3.36 dB
Cable attenuation
2.56 dB
Attenuation per 100 m at this frequency
2.85 dB
Share of power retained
46.116%

Step by step

  1. 1Values used
  2. 2Attenuation
  3. 3Total attenuation= 3.36 dB
  4. 4Cable attenuation= 2.56 dB
  5. 5Attenuation per 100 m at this frequency= 2.85 dB
  6. 6Share of power retained= 46.116

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax or fees or charges into account.
  • Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why does frequency matter for copper?

Skin effect and dielectric loss both increase with frequency, so the same cable attenuates a 500 MHz signal far more than a 100 MHz one.

What does 3 dB actually mean?

A halving of power. Every additional 3 dB halves it again, so 10 dB leaves a tenth and 20 dB leaves a hundredth.

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