Enter the apparent power (watts) and the reactive power (watts) into the calculator to determine the Active Power.

## Active Power Formula

The following formula is used to calculate the Active Power.

**Pa = SQRT ( AP^2 – RP^2)**

- Where Pa is the Active Power (watts)
- AP is the apparent power (watts)
- RP is the reactive power (watts)

## How to Calculate Active Power?

The following two example problems outline how to calculate the Active Power.

**Example Problem #1:**

- First, determine the apparent power (watts). In this example, the apparent power (watts) is measured to be 40.
- Next, determine the reactive power (watts). For this problem, the reactive power (watts) is calculated to be 20.
- Finally, calculate the Active Power using the formula above:

Pa = SQRT ( AP^2 – RP^2)

Inserting the values from above and solving the equation with the imputed values gives:

Pa = SQRT (40^2 – 20^2) = 34.64 (watts)

**Example Problem #2: **

Using the same process as example problem 1, we first define the variables outlined by the formula. In this case, the values are:

apparent power (watts) = 70

reactive power (watts) = 20

Entering these values into the formula or calculator above gives us: Pa = SQRT ( 70^2 – 20^2) = 67.08 (watts)