Enter the input current and voltage and the output current and voltage into the calculator to determine the transformer loss.

Transformer Loss Formula

The following equation is used to calculate the Transformer Loss.

TL = Ii * Vi – Io*Vo

  • Where TL is the transformer power loss (watts)
  • Ii is the input current (amps)
  • Vi is the input voltage (volts)
  • Io is the output current (amps)
  • Vo is the output voltage (volts).

To calculate the transformer loss, subtract the output power from the input power.

What is a Transformer Loss?


A transformer loss is defined as a loss in power through the inefficiencies found within the process of a transformer stepping up or down the voltage and current of a system.

How to Calculate Transformer Loss?

Example Problem:

The following example outlines the steps and information needed to calculate Transformer Loss.

First, determine the input current and voltage. For this example, these are 120 amps and 80 volts respectively.

Next, determine the output current and voltage. In this case, these are 100 amps and 90 volts respectively.

Finally, calculate the transformer loss using the formula above:

TL = Ii * Vi – Io*Vo

TL = 110*80 – 100*90

TL = 600 Watts