Insertion Loss Calculator

Written by Great Medico

Updated September 25, 2026 •2 min read

Share Print Save

A insertion loss result can look convincing even when one unit or assumption is off. Electrical and magnetic results can shift sharply with geometry, frequency, phase, material properties, and whether the quantity is a magnitude or signed value. This page keeps the calculation narrow enough to trace the answer back to the values you enter.

What this calculator does

The Insertion Loss Calculator connects Power/voltage before insertion, Power/voltage after insertion, Insertion loss to the page’s insertion loss. Supporting values are included only when they follow from the same relationship, so you can compare the headline with the quantities behind it.

How to use it

Enter Power/voltage before insertion, Power/voltage after insertion, Insertion loss using the units shown beside each field. Set I want to calculate… to match the solve path you want. Keep all values from the same physical case, then check the headline result and any supporting values before changing one input at a time for comparison.

How the calculation works

Insertion loss is 10log10(before/after) for power quantities and 20log10(before/after) for voltage quantities. The selector determines which logarithmic factor is used.

Example

If power is 10 W before a device and 5 W after it, insertion loss is 10log10(10/5) ≈ 3.01 dB. If those same numbers represent voltage under compatible impedance conditions, the voltage-mode formula gives about 6.02 dB because it uses 20log10.

How to interpret the result

Read the insertion loss with its sign, magnitude, phase, frequency, geometry, and unit as applicable. A field, reactance, power factor, loss, or flux value should be compared only with a quantity defined in the same way.

Limitations and notes

Real electrical and magnetic systems can add parasitics, finite geometry, temperature dependence, nonlinear materials, frequency-dependent losses, tolerances, and measurement uncertainty beyond the ideal relationship shown here. Recheck Power/voltage before insertion, Power/voltage after insertion first if the result looks surprising, because an incorrect unit or definition there can dominate rounding error. Safety-critical or standards-based work still needs the applicable design rules and independent verification.