Wattage to Amperage Calculator

Created by Purnima Singh, PhD
Reviewed by Rahul Dhari
Last updated: Apr 10, 2022

Omni's wattage to amperage calculator allows you to calculate the current through an AC or DC circuit from power and voltage values.

If you have ever wondered how to convert watts to amps, i.e., power to current for a given circuit, you have come to the right place.

Continue reading to learn how to calculate amperage from wattage and voltage for various circuit types. You will also find an example of using this wattage voltage amperage calculator.

Before going any further, let us understand what exactly we mean by the terms wattage, voltage, and amperage.

Wattage, voltage, and amperage

There is production or dissipation of power by the circuit elements (e.g., resistors) in every electrical circuit. We can express the power dissipation by the equation:

P=VI\small P = VI

where:

  • PP - Power or wattage dissipated by the circuit element expressed in watts (W);
  • II - Current or amperage through the circuit element measured in units called amperes (A); and
  • VV - Voltage across the element expressed in the unit volts (V).

Thus, when we talk about calculating amperage from wattage or converting wattage to amperage, we simply mean using the above equation to calculate the current from power and voltage values.

How to calculate amperage from wattage

To calculate the current or voltage from power, we first need to know the circuit type, i.e., AC or DC. Then we can use one of the formulae given below to convert watts to amps:

For DC circuit, the relation between power (PP), voltage (VV) and current (II) is given as:

P=VI\small P = VI

For the single-phase AC circuit, we can use the following formula to convert watts to amps:

IRMS=PavgVRMS×PF\small I_{RMS} = \frac{P_{avg}}{V_{RMS} \times PF}

Where:

  • IRMSI_{RMS} - Root mean square current;
  • PavgP_{avg} - Average power;
  • VRMSV_{RMS} - Root mean square voltage; and
  • PFPF - Power factor, which is the ratio between the real and apparent power in a circuit.

Not sure how to calculate power factor? Worry not! We have a tool for that too.

If the circuit is a three-phase AC circuit, we can use the formulae:

IRMS=Pavg3×VRMS×PF,for line-to-line voltage; andIRMS=Pavg3×VRMS×PF,for line-to-neutral voltage.\scriptsize \begin{align*} I_{RMS} &= \frac{P_{avg}}{\sqrt{3} \times V_{RMS} \times PF}, \\ &\text{for line-to-line voltage; and} \\ I_{RMS} &= \frac{P_{avg}}{3 \times V_{RMS} \times PF},\\ &\text{for line-to-neutral voltage.}\\ \end{align*}

How to use the wattage to amperage calculator?

Let us calculate the amperage of an electrical appliance using 1500 watts of power and running on a 120 V DC circuit:

  1. Using the drop-down menu, choose the current type as DC.

  2. Enter the power as 1500 W and voltage as 120 V.

  3. The calculator will convert 1500 watts to amps for the given condition and show the resulting current as 12.5 A.

Other similar calculators

If you find this voltage amperage calculator useful, do check out our other similar tools:

FAQ

How does wattage relates to amperage for AC single-phase circuit?

For an AC single-phase circuit, the relation between power in wattage (P) and current in amperage (I) is given by the formula:
I = P / (V × PF ). Here PF is the power factor, and V is the RMS (root mean square) voltage in volts.

How do I calculate amperage from wattage and voltage for DC circuit?

To calculate amperage from wattage and voltage for the DC circuit, follow the given instructions:

  1. Divide the power in wattage (W) by the voltage in volts (V).

  2. Congrats! You have calculated the amperage from wattage and voltage.

Purnima Singh, PhD
Current type
DC
Power (P)
W
Voltage (V)
V
Amperage (I)
A
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