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Insertion Loss from Power or Equal-Impedance Voltage

Calculate insertion loss from power or equal-impedance voltage using known measurements, selectable units and clear physical assumptions.

  • Formula & worked example
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Calculator inputs

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How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

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Formula and method

Reducing delivered power from 100 W to 10 W gives insertion loss 10 dB.

Lₚ = 10 log₁₀(Pbefore/Pafter); Lᵥ = 20 log₁₀(Vbefore/Vafter)

Worked example

Enter these known values and leave the other values blank.

Power before insertion
100 W
Power after insertion
10 W
Insertion loss
10 dB

Assumptions and limitations

  • The voltage method assumes unchanged load impedance and comparable RMS amplitudes. Positive loss indicates attenuation; a negative result indicates gain. All measured powers or amplitudes must be positive.
  • Enter mutually consistent measurements and clear a quantity before inferring it. Calculations use 64 significant digits; the displayed result is rounded separately.

Common questions

Can I use voltage measurements instead of power?

Choose the voltage mode. Its 20 log₁₀ voltage ratio represents the power ratio only when the compared impedances are equal. For unequal impedances, use the delivered-power method.

References

The calculation equations, inverse formulas, units, and input rules were imported from this source. Bookify provides the interface and equation solver.

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