Calculate full-load current or rated power for DC, single-phase, and three-phase loads and motors using voltage, kW, kVA, horsepower, power factor, and efficiency.

ARated Load Current Tool
Required: motor output power, line-to-line voltage, power factor, and efficiency.
V
kW
A
%
Estimated full-load current
—
Electrical input—
Apparent power—
Motor output—
Supply—
Power factor—
Efficiency—
—
This is a formula-based estimate for balanced, sinusoidal rated operation. Use the equipment nameplate current and applicable electrical code for conductor, overload, fuse, breaker, or starter sizing. Starting current, harmonics, voltage unbalance, service factor, derating, and installation conditions are not included.

Full Load Current Formula

The following formula is used to calculate the Full Load Current. 

Single Phase: I = P / (V · PF)

Three Phase: I = P / (√3 V · PF)

  • Where If is the Full Load Current (amps)
  • Pf is the full load power (watts) 
  • Vf is the full load voltage (volts) 

To calculate full load current, divide the full load power by the product of the full load voltage times 1.723.

How to Calculate Full Load Current?

The following two example problems outline how to calculate the Full Load Current.

Example Problem #1:

  1. First, determine the full load power (watts). In this example, the full load power (watts) is measured to be 67.
  2. Next, determine the full load voltage (volts). For this problem, the full load voltage (volts) is calculated to be 8.
  3. Finally, calculate the Full Load Current using the formula above: 

If = Pf/(1.732*Vf)

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

If = 67/(1.732*8) = 4.83 (amps)

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:

full load power (watts) = 90

full load voltage (volts) = 4

Entering these values into the formula above gives : 

If = 90/(1.732*4) = 12.99 (amps)