Insertion Loss Calculator

Enter your input power and output power (or voltage levels) to calculate the insertion loss of a two-port network in decibels. Switch between power-based and voltage-based modes, or compute cascaded losses across multiple stages. Your results include insertion loss (dB), transmission coefficient, and linear loss factor. Also try the Watts to Amps Calculator.

mW

Power delivered to the network from the source

mW

Power delivered to the load after the network

V

Voltage at the input port of the network

V

Voltage at the output port of the network

Enter individual insertion loss values in dB for each cascaded stage

Results

Insertion Loss

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Transmission Coefficient (T)

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Linear Loss Factor

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Power Lost

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Power Transmitted

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Results Table

Frequently Asked Questions

What is insertion loss?

Insertion loss is the reduction in signal power that occurs when a component or network is inserted into a transmission line. It is expressed in decibels (dB) and quantifies how much power is lost due to reflection, absorption, or dissipation within the inserted device. A lower insertion loss value indicates a more transparent device. See also our calculate Impedance.

How do I calculate insertion loss?

Insertion loss is calculated using the formula IL = 10 × log₁₀(P_in / P_out) when working with power values, or IL = 20 × log₁₀(V_in / V_out) when working with voltage levels. Both formulas yield a result in decibels (dB). A positive dB value always means power has been lost through the network.

What is the insertion loss if 90% of the power is transmitted?

If 90% of the power is transmitted, the output power is 0.9 times the input power. Applying the formula: IL = 10 × log₁₀(1 / 0.9) ≈ 0.46 dB. This means a 10% power loss corresponds to roughly 0.46 dB of insertion loss.

What causes insertion loss?

Insertion loss is caused by several factors including impedance mismatch between the device and the transmission line (causing signal reflection), dielectric absorption within the material, conductor resistance, and radiation losses. In connectors and cables, poor contact and material imperfections are common contributors. You might also find our calculate Resistor Wattage useful.

How is insertion loss related to frequency?

Insertion loss generally increases with frequency. At higher frequencies, skin effect increases conductor resistance, dielectric losses in insulating materials rise, and connector imperfections become more significant relative to the signal wavelength. This is why RF and microwave components are always characterized across a frequency range.

What is cascaded insertion loss?

When multiple components (e.g., cables, connectors, filters) are connected in series, their insertion losses add together in decibels. For example, three components with losses of 1.5 dB, 2.0 dB, and 0.8 dB produce a total cascaded insertion loss of 4.3 dB. This additive property makes the dB scale particularly convenient for system link budget analysis.

What is the difference between insertion loss and return loss?

Insertion loss measures how much signal power is lost as it passes through a device, while return loss measures how much signal power is reflected back toward the source due to impedance mismatch. Both are expressed in dB. A good component has low insertion loss (minimal forward attenuation) and high return loss (minimal reflection).

What is the transmission coefficient and how does it relate to insertion loss?

The transmission coefficient (T) is the ratio of output power to input power, expressed as a linear (non-dB) value between 0 and 1. It relates to insertion loss by the formula T = 10^(−IL/10). For example, an insertion loss of 3 dB corresponds to a transmission coefficient of approximately 0.5, meaning half the input power reaches the output.