KVA to Amps Calculator
Convert apparent power in kilovolt-amperes (kVA) to current in amperes (A). Enter the power and voltage, and the calculator returns both single-phase and three-phase current.
Electrical Power Conversion: kVA to Amps
kVA to Amps Formula
Where:
- \(S\) — apparent power (kVA)
- \(V\) — voltage (V)
- \(I\) — current (A)
The first formula applies to single-phase systems; the second to three-phase systems, where the factor \(\sqrt{3} \approx 1.732\) accounts for the phase relationship between the three conductors.
kVA to Amps – Calculation Example
Example: a load with an apparent power of 10 kVA connected to a 220 V supply.
Single phase:
\[ I = \frac{1000 \cdot 10}{220} = 45.45~\mathrm{A} \]
Three phase (line-to-line voltage):
\[ I = \frac{1000 \cdot 10}{\sqrt{3} \cdot 220} = \frac{10000}{381.05} \approx 26.24~\mathrm{A} \]
Result: the single-phase current is approximately 45.45 A, and the three-phase current is approximately 26.24 A.
How to Use the Calculator
- Enter the apparent power in the Power field, in kilovolt-amperes (kVA).
- Enter the Voltage in volts (V). For three-phase systems, use the line-to-line voltage.
- Read the results: the Single Phase Current and the Three Phase Current, both in amperes (A).
Both currents are calculated at once, so you can compare the two system types for the same power and voltage. The voltage must be greater than zero — the calculator shows an error message otherwise.
What Are kVA and Amps?
kilovolt-amperes (kVA) measure apparent power — the total power that a source delivers to a load. Amperes (A) measure current — the flow of electric charge through the conductors. The two are related through voltage: for a fixed apparent power, a higher voltage means a lower current, and vice versa. Converting between them is a routine task when sizing generators, transformers, cables, and protective devices.
Converting kVA to amps matters because electrical components are rated in amps, not in kVA. A circuit breaker, a cable's ampacity, and a busbar's capacity are all expressed as maximum current. Once you know the current drawn by a load, you can select conductors and protection with adequate margins. For example, a 10 kVA load on a single-phase 220 V line draws about 45.5 A, which already requires fairly heavy cable compared with a three-phase connection at the same power.
The reason three-phase systems draw less current per unit of power is that the three phases share the load and are offset by 120°. The total three-phase power is \(\sqrt{3}\) times the product of line voltage and line current, so the current is reduced by that same factor. This is why industrial equipment, motors, and large installations almost always use three-phase supply.
Note that kVA is apparent power, not real power. Real power in kilowatts (kW) equals kVA multiplied by the power factor. Current calculated from kVA represents the full current the conductors must carry regardless of the load's power factor, which is exactly what you need for cable and breaker sizing. To work with real and reactive power instead, see the Real and Reactive Power Calculator.
Quick Reference Table
| kVA | Current at 220 V, single-phase (A) | Current at 400 V, three-phase (A) |
|---|---|---|
| 5 | 22.73 | 7.22 |
| 10 | 45.45 | 14.43 |
| 25 | 113.64 | 36.08 |
| 50 | 227.27 | 72.17 |
| 100 | 454.55 | 144.34 |
Assumptions, Limitations and Practical Tips
- Line-to-line voltage for three-phase: the three-phase formula assumes the entered voltage is the line-to-line voltage (e.g. 400 V in Europe, 208 V or 480 V in North America). If you only know the line-to-neutral voltage, use the single-phase result for each phase conductor.
- Resistive vs. reactive loads: the calculation is independent of the power factor because kVA already includes it. However, if you are starting from kW instead of kVA, divide by the power factor first to get kVA.
- Margin for sizing: when selecting cables and breakers, add a safety margin above the calculated current (typically 20–25%) and account for motor starting currents, which can be several times the running current.
- Voltage drop: long cable runs add voltage drop, which increases the current for the same power. Keep cable lengths short or upsize the conductors; once the current is known, the Wire Gauge Calculator helps with conductor selection.
- Transformer rating: transformer nameplates state kVA, so this conversion tells you the secondary current the transformer must deliver. For transformer-specific calculations, see the Single Phase Transformer Calculator.
Frequently Asked Questions
How do I convert kVA to amps by hand?
Multiply the kVA value by 1000, then divide by the voltage. For single phase: \( I = \frac{S \times 1000}{V} \). For three phase, also divide by \( \sqrt{3} \approx 1.732 \): \( I = \frac{S \times 1000}{1.732 \times V} \). For example, 15 kVA at 240 V single phase gives \( \frac{15000}{240} = 62.5 \) A.
How many amps is a 3.5 kVA generator at 120 V?
Divide 3500 by 120 to get about 29.2 A. Keep in mind that this is the total apparent power rating; if the generator has multiple outlets, the current is distributed among them, and each individual socket is limited by its own breaker (typically 15 or 20 A). Also avoid running the generator at 100% load continuously — stay at 80% or less for reliability.
Why is the three-phase current lower than the single-phase current?
In a three-phase system the load is shared across three conductors whose voltages are offset by 120°. The total power equals \( \sqrt{3} \times V \times I \), so the current per conductor is reduced by the factor \( \sqrt{3} \approx 1.732 \) compared with a single-phase circuit at the same voltage. That is why the same kVA draws about 58% of the single-phase current.
Should I use line-to-line or line-to-neutral voltage for three phase?
The three-phase formula assumes line-to-line voltage, such as 400 V in Europe or 208 V and 480 V in North America. If you only know the line-to-neutral voltage (e.g. 230 V in a 400 V system), either multiply it by \( \sqrt{3} \) to get the line-to-line value, or use the single-phase formula per phase — both give the same per-conductor current.
How do I convert amps back to kVA?
Reverse the formula: multiply current by voltage and divide by 1000. Single phase: \( S = \frac{I \times V}{1000} \). Three phase: \( S = \frac{\sqrt{3} \times I \times V}{1000} \) using line-to-line voltage. For instance, 30 A at 240 V single phase equals 7.2 kVA. This is useful when checking whether a transformer or generator can handle a measured load.
What is the difference between kVA and kW when calculating current?
kVA is apparent power; kW is real power, equal to kVA multiplied by the power factor. Current must be calculated from kVA, because conductors and breakers carry the full current regardless of the power factor. If you only know kW, divide by the power factor first: a 10 kW load with a power factor of 0.8 is 12.5 kVA, and the current should be computed from that larger figure.
What are common mistakes when converting kVA to amps?
The most frequent errors are: using line-to-neutral voltage in the three-phase formula (this understates current by \( \sqrt{3} \)); confusing kVA with kW and forgetting to divide by the power factor; forgetting to multiply kVA by 1000 when working in volts; and sizing cables exactly at the calculated current with no margin. Always add 20–25% headroom and consider motor inrush current, which can be 5–7 times the running current.