kVA Calculator

Created by Kenneth Alambra
Reviewed by Wojciech Sas, PhD candidate and Jack Bowater
Last updated: Sep 24, 2022

This kVA calculator will help you determine the apparent power over a particular operating voltage and current. Similarly, it also works as volts and amps to kVA calculator. As an added feature, this tool can also function as a kVA to kW calculator to help you easily convert kVA to kW or kVA to watts.

In this tool, you will learn what kVA means, the difference between kVA and kW, and how to calculate kVA using the apparent power formulas. Keep on reading to start learning.

What does kVA mean?

Kilovolt-amps, abbreviated as kVA, is the typical unit of measure for what is called apparent power. Apparent power is the amount of electrical power produced by an electrical system at a particular applied voltage and current. Following the Ohm's law formula, we can obtain the amount of electrical power by multiplying the amount of voltage by the current flow through any electrical system.

Since we measure voltage in units of volts and current in units of amperes, we can put these together to express power in terms of units of volt-amperes. Although we already have watts as the unit measure of power, we still use volt-amperes for a particular reason that we'll discuss next.

What is the difference between kVA and kW?

The main difference between kilovolt-amperes and kilowatts, or volt-amperes and watts, is the presence of a known value called the power factor. The power factor is the ratio between the real power (measured in watts) and the apparent power. In other words, the power factor determines the amount of apparent power converted to real power. We can express this relationship in equation form, as shown below:

power factor=real powerapparent power\small \text{power factor} = \frac{\text{real power}}{\text{apparent power}}

The value of the power factor (abbreviated to PF) depends on what kind of load the electrical unit is drawing from the electrical system. Electrical systems like transformers, generators, pumps, and motors provide power for various people's requirements, and we sometimes do not know the value of the power factor to be able to rate these electrical systems in watts. That is the reason why we use volt-amperes or kilovolt-amperes.

🙋 We have a separate power factor calculator if you want to dive deeper into that topic.

In an ideal system, we have 1 (or 100%) as the power factor's value. In that case, we can say that the real or actual power is equal to the apparent power. You can learn more about actual power in our watts to amps calculator.

How do I calculate kVA?

Now that we understand the significance of using kVA let us learn how to calculate the kVA apparent power given an applied voltage and current. Estimating the apparent power is quite simple. However, we have to consider that we can observe apparent power in three different power systems' cases. Below are the three different apparent power formulas we can use for each of those cases:

  • Single-phase power system

S=I×V1000S = I\times \frac{V}{1000}

  • 3-phase power system with line-to-line voltage

S=3×I×VL-L1000S = \sqrt{3}\times I\times \frac{V_\text{L-L}}{1000}

  • 3-phase power system with line-to-neutral voltage

S=3×I×VL-N1000S = 3\times I\times \frac{V_\text{L-N}}{1000}


  • SS is the apparent power in kVA;
  • II is the current amperage in amperes;
  • VV is the voltage in volts;
  • VL-LV_\text{L-L} is the line-to-line voltage in volts; and
  • VL-NV_\text{L-N} is the line-to-neutral voltage in volts.

Sample volts and amps to kVA calculation

For our first example, let us consider a transformer drawing power from a single-phase 240-volt power source at a current of 10 amperes. To determine the apparent power (S1\small S_1) we can get from this transformer, we have to use the first equation in our list of apparent power formulas and substitute these given values as follows:

S1=I×V1000=10 A×240 V1000=2400 VA1000=2.4 kVA\small \begin{align*} S_1 &= I\times \frac{V}{1000}\\[1.0 em] &= 10\ \text{A}\times \frac{240\ \text{V}}{1000}\\[1.0 em] &= \frac{2400\ \text{VA}}{1000}\\[1.0 em] &= 2.4\ \text{kVA} \end{align*}

We can now say that we can have at most 2.4 kVA of apparent power from the electrical system that we are considering in our calculation. If our power source was being delivered over a 3-phase power system with a line-to-line total voltage of 240 V at a current of 10 amperes, we can use the second formula to find the new apparent power (S1\small S_1), as we can see below:

S2=3×I×VL-L1000=3×10 A×240 V1000=4156.9219 VA1000=4.157 kVA\small \begin{align*} S_2 &= \sqrt{3}\times I\times \frac{V_\text{L-L}}{1000}\\[1.0 em] &= \sqrt{3}\times10\ \text{A}\times \frac{240\ \text{V}}{1000}\\[1.0 em] &= \frac{4156.9219\ \text{VA}}{1000}\\[1.0 em] &= 4.157\ \text{kVA} \end{align*}

And that is how to calculate kVA with a given voltage and amperage for a particular system. 🙂

💡 With our kVA calculator, you can calculate multiple setups in no time. If you have the value for the power factor and want to find the electrical system's real power output, activate the advanced mode of our kVA calculator to display the kVA to kW calculator. Once you're there, simply input the needed values to convert kVA to kW or convert kVA to watts, whichever unit you want.

Want to learn more?

If you are wondering how much your power consumption is for any time duration, you can find out using our electricity cost calculator. Check it out to see how much your appliances, like your air conditioner and fan, contribute to your electric bill.


How do I convert kVA to amps?

  1. Find the voltage of the system.
  2. Then, multiply the apparent power in kVA by 1,000 to obtain a value in VA (volt-amps).
  3. Finally, divide the VA value by the system's voltage in volts.

By doing the above steps, you will easily find the system's current in amps.

What is the difference of kVA and kW?

The main difference between kVA and kW is the presence of a value called the power factor. Once the power factor is known, we get to express the system's power output in kW. Without the power factor, it would be safe to rate an electrical system like a generator or a transformer in kVA. Using kVA indicates we are still talking about the system's potential or apparent power.

How do I convert kVA to kW?

You can convert kVA to kW by multiplying your known kVA value by your electrical system's power factor. It is also good to remember that the converted kW will never be greater than the apparent power in kVA since the power factor's value only ranges from 0 to 1.

What does 500 kVA mean on my 500 kVA generator?

It means that you can draw up to 500 kW of power from your generator. However, you could also draw less power depending on how you want to use your 500 kVA generator or the power factor of your electrical system.

What can I do with a 500 kVA generator?

You can already do a lot with a 500 kVA generator. You can use it to run a small house with the typical household appliances, including a refrigerator, some water heaters, and even an air conditioner, all running simultaneously. But, if you only need to run the essential appliances at home intermittently, it's worth noting that a 10 kVA generator is already sufficient.

Kenneth Alambra
Input values
Load distribution
Single phase
Voltage (V)
Current (I)
Output value
Apparent power (S)
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