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Enter values, select units, and then click **Convert**.

Voltage:

Current:

Apparent Power:

Active or Real Power:

This tool can be used for basic electrical power calculations and conversion between different power units (A, kA, W, kW, VA, kVA, BTU/h).

Note: All calculations are performed for a single phase alternating current (AC) circuit.

**Power Factor:** In an AC electrical power system the power factor is defined as the ratio of the real power,
measured in watts (W), and the apparent power, measured in VA (volt-amperes) that the load draws.
For a load circuit the power factor can get values in the range from 0 to 1.
Traditional computer power supplies used to have power factors between 0.6 and 0.7.
Modern power supplies for personal computers, servers, etc. operate with power factor close to 1.
For example, 80 PLUS Certified power supplies have power factor in the range between 0.85 and 1.0.

**Calculation formulas**

**Current:**

The phase current I in amps (A) is equal to the real power P in watts (W), divided by the product of the power factor PF and the RMS voltage V in volts (V):
*I* = *P* / (*PF* * *V*)
The phase current I in amps (A) is equal to the apparent power S in volt-amps (VA), divided by the RMS voltage V in volts (V):
*I* = *S* / *V*

**Apparent Power:**

The apparent power S in volt-amps (VA) is equal to the product of the voltage V in volts (V) and the current I in amps (A):
*S* = *V* * *I*
The apparent power S in volt-amps (VA) is equal to the real power P in watts (W) divided by the power factor PF:
*S* = *P* / *PF*

**Active or Real Power:**

The power P in watts (W) is equal to the product of the phase current I in amps (A), the RMS voltage V in volts (V), and the power factor PF:
*P* = *I* * *V* * *PF*
The real power P in watts (W) is equal to the product of the apparent power S in volt-amps (VA) and the power factor PF:
*P* = *S* * *PF*

**Heating/Cooling:**

The formula to convert power in watts (W) into BTU_{(IT)} per hour (BTU/h):
*P _{(BTU/h)}* =

**See also:**

80 PLUS Certified Power Supplies and Manufacturers

Wikipedia British thermal unit article