kVA to Amps Calculator | Single Phase & Three Phase Conversion with Formula
kVA to Amps Calculator
Converting kVA to amps requires only two inputs like the voltage and phase. Single-phase divides by voltage alone. Three-phase divides by voltage times √3 (1.732). Power factor is not required when you already have kVA. Use the calculator above or the formulas and tables below for 480V, 400V, 208V, and 240V systems.
Common kVA to Amps Conversions
| kVA | 230V 1-Phase | 400V 3-Phase | 480V 3-Phase |
|---|---|---|---|
| 5 kVA | 21.7 A | 7.2 A | 6.0 A |
| 10 kVA | 43.5 A | 14.4 A | 12.0 A |
| 25 kVA | 108.7 A | 36.1 A | 30.1 A |
| 50 kVA | 217.4 A | 72.2 A | 60.1 A |
| 100 kVA | 434.8 A | 144.3 A | 120.3 A |
| 250 kVA | 1087 A | 360.8 A | 300.7 A |
| 500 kVA | 2174 A | 721.7 A | 601.4 A |
Generator kVA to Amps Chart
| Generator Size | 400V 3-Phase | 480V 3-Phase |
|---|---|---|
| 25 kVA | 36.1 A | 30.1 A |
| 50 kVA | 72.2 A | 60.1 A |
| 100 kVA | 144.3 A | 120.3 A |
| 250 kVA | 360.8 A | 300.7 A |
| 500 kVA | 721.7 A | 601.4 A |
Transformer kVA to Amps (Common Sizes)
| Transformer | 480V Primary | 208V Secondary |
|---|---|---|
| 15 kVA | 18.0 A | 41.6 A |
| 30 kVA | 36.1 A | 83.3 A |
| 45 kVA | 54.1 A | 125 A |
| 75 kVA | 90.2 A | 208 A |
| 112.5 kVA | 135.3 A | 312 A |
Note: Values are approximate at unity power factor. Always confirm with actual nameplate data and local electrical codes.
Voltage Drop CalculatorkVA to Amps Calculator: How to Convert kVA to Amps
You must required the right voltage and phase type to convert kVA to amps. Single-phase and three-phase systems use different formulas.
Single-phase divides kVA by voltage. Three-phase divides by voltage times 1.732.
[Calculator Tool Positioned Here]
kVA to Amps Formula
The math changes based on your electrical setup.
Single-phase:
Three-phase:
Where:
- I = current in amperes
- kVA = apparent power in kilovolt-amperes
- V = voltage in volts (line-to-line for three-phase)
- sqrt(3)= approximately 1.732
We multiply by 1000 because 1 kVA equals 1000 VA.
How to Convert kVA to Amps
Here is the process for conversion:
- Check your equipment nameplate for the kVA rating.
- Find the system voltage. Three-phase equipment uses line-to-line voltage.
- Confirm if it’s single-phase or three-phase.
- Plug the numbers into the correct formula.
- Round your answer as needed.
Single-Phase kVA to Amps
Single-phase is simpler. Just voltage and power.
Formula:
Example 1:
25 kVA transformer at 240 V.
Example 2:
10 kVA UPS at 120 V.
You’ll see single-phase in homes and small commercial buildings. Common voltages are 120 V, 208 V, 230 V, and 240 V.
Three-Phase kVA to Amps
Three-phase carries power across three wires. It’s more efficient than single-phase.
Formula:
The (\sqrt{3}) factor (1.732) comes from how power splits across three conductors in balanced systems.
Example 1:
100 kVA transformer at 480 V.
Example 2:
75 kVA load at 208 V.
Always use line-to-line voltage for three-phase. That’s the voltage between any two phase conductors. Don’t use line-to-neutral voltage in this formula.
kVA to Amps Chart
Quick reference for common industrial voltages.
Single-Phase kVA to Amps
| kVA | 120V | 208V | 240V |
| 1 | 8.3 A | 4.8 A | 4.2 A |
| 5 | 41.7 A | 24.0 A | 20.8 A |
| 10 | 83.3 A | 48.1 A | 41.7 A |
| 25 | 208.3 A | 120.2 A | 104.2 A |
| 50 | 416.7 A | 240.4 A | 208.3 A |
| 75 | 625.0 A | 360.6 A | 312.5 A |
| 100 | 833.3 A | 480.8 A | 416.7 A |
Three-Phase kVA to Amps
| kVA | 208V | 400V | 480V |
| 10 | 27.8 A | 14.4 A | 12.0 A |
| 25 | 69.4 A | 36.1 A | 30.1 A |
| 50 | 138.9 A | 72.2 A | 60.2 A |
| 75 | 208.3 A | 108.3 A | 90.2 A |
| 100 | 277.7 A | 144.3 A | 120.3 A |
| 150 | 416.6 A | 216.5 A | 180.4 A |
| 200 | 555.5 A | 288.7 A | 240.6 A |
| 250 | 694.4 A | 360.8 A | 300.7 A |
Use these for quick estimates. Double-check your math for critical installations.
How Voltage Changes the Current
Same kVA at different voltages gives different current. Lower voltage means higher current.
Example:
100 kVA three-phase at different voltages.
At 208 V:
At 400 V:
At 480 V:
For the same kVA load, higher voltage results in lower current. This can reduce the required conductor ampacity and equipment current rating, subject to the applicable design and code requirements.
The relationship is inverse. Double the voltage, current drops by half.
Transformer kVA to Amps
Transformers have different current on each side when voltages differ. The kVA stays the same.
Example:
75 kVA three-phase transformer.
- Primary = 480 V
- Secondary = 208 V
Primary current:
Secondary current:
Secondary current is higher because secondary voltage is lower. This is normal.
The kVA capacity is 75 on both sides. We’re ignoring transformer losses here.
Size your wires and breakers for each side separately. Primary needs protection for 90.2 A. Secondary needs protection for 208.2 A.
Transformer nameplates show kVA, primary voltage, secondary voltage, and sometimes the full-load current for each winding. Check your nameplate first.
Generator kVA to Amps
Generators use kVA ratings because they deliver both real and reactive power.
Example:
500 kVA generator, 400 V, three-phase.
This is full-load current at rated voltage. Your actual current depends on what’s connected.
Generator nameplates list kVA, voltage, power factor, and rated current. Some show kW at a specific power factor too.
The kVA rating is the max apparent power the generator can make without overheating.
Picking a generator involves more than just kVA. You need to think about starting currents, harmonics, and unbalanced loads. The calculated current helps size output wires and breakers, but there’s more to generator selection.
UPS kVA to Amps
UPS systems get rated in kVA. They often have separate kW ratings because of power factor limits.
Example:
20 kVA UPS, 208 V, three-phase.
Output current at full load:
Input current can differ from output current. It depends on UPS type, battery charging, and efficiency.
Double-conversion UPS pulls input current based on output load plus losses and battery charging.
Check the manufacturer’s specs for input current. The formula above works for output current when the UPS delivers full rated kVA.
Does Power Factor Affect kVA to Amps?
No. Power factor doesn’t go in the basic kVA-to-amps formula and kVA to Amps calculator.
kVA is apparent power. It’s the total power in an AC circuit, including working power and reactive power.
kW is real power. That’s the actual power doing work.
Power factor connects them.
Where (PF) is power factor, between 0 and 1.
Converting kVA to amps doesn’t need power factor. The kVA already accounts for total current.
Converting kW to amps needs power factor.
Single-phase:
Three-phase:
Don’t add power factor to kVA-to-amps. That’s wrong and gives bad results.
kVA vs kW
Know the difference so you don’t mix them up.
| What it is | kVA | kW |
| Name | Apparent power | Real power |
| Unit | Kilovolt-amperes | Kilowatts |
| Includes reactive power | Yes | No |
| Used for | Equipment ratings, transformer capacity, generator capacity | Work output, energy bills |
| Needs power factor | No | Yes (for conversions) |
kVAR is reactive power. Motors and transformers need it to make magnetic fields.
These three relate like this:
Resistive loads have power factor = 1, so kVA equals kW.
Industrial loads with motors usually have power factor between 0.7 and 0.95. That means kVA is bigger than kW.
Common kVA to Amps Calculation Mistakes
Don’t make these errors.
Wrong formula for phase type
Using single-phase math on three-phase gives you 1.732 times too much. Check phase first.
Forgetting 1.732
Leaving out sqrt{3} in three-phase gives bad answers. It comes from the geometry of balanced three-phase power.
Wrong voltage type
Three-phase formula needs line-to-line voltage. In a 480 V three-phase system, use 480 V. Don’t use 277 V (line-to-neutral) unless you change the formula.
Adding power factor wrongly
Power factor converts kW to kVA, not kVA to amps. Don’t put it in the kVA to amps formula.
Mixing transformer sides
Each transformer side has different voltage and different current. Calculate them separately.
Thinking calculated amps = breaker size
The number you get is full-load current. Breaker sizing also involves continuous load rules, temperature, wire size, fault current, and code rules.
Treating kVA like kW
They’re different unless power factor is 1. Equipment rated in kVA can deliver that apparent power at any power factor, but real power depends on the load.
Ignoring nameplate
Nameplates give tested values. Calculations assume perfect balanced conditions. When you have nameplate current, use it.
Can kVA to Amps Be Used for Breaker or Cable Sizing?
It’s a starting point, not the final answer.
Breakers
Calculated full-load current is one input used when selecting a breaker. The final breaker rating depends on the load, equipment, conductor ampacity, fault current, protection requirements, and applicable code.
100 A calculated doesn’t automatically mean 100 A breaker. You might need 125 A or bigger.
Cables
Calculated current helps find minimum wire size. But you also need temperature correction, conduit fill derating, voltage drop, terminal temperature limits, and parallel conductor rules if applicable.
100 A load doesn’t mean exactly 100 A wire. Installation conditions might need bigger wire.
Motors
Motors have high starting current, service factor, and thermal characteristics. Use motor full-load current from NEC tables or manufacturer data, not a generic kVA-to-amps calc.
Load studies
kVA-to-amps helps estimate current for load studies, panel schedules, and feeder sizing. Combine it with demand factors, diversity factors, and future expansion allowances per code.
Electrical design needs engineering judgment and code compliance. Calculated current is one piece of a bigger puzzle.
Frequently Asked Questions
How many amps is 100 kVA?
Depends on voltage and phase. 100 kVA three-phase at 480 V = 120.3 A. At 208 V three-phase = 277.7 A. Single-phase at 240 V = 416.7 A.
What’s the three-phase kVA to amps formula?
Multiply kVA by 1000, divide by 1.732 times line-to-line voltage. Result is line current in amperes.
Do I need power factor to convert kVA to amps?
No. kVA already represents apparent power. Power factor is for converting between kW and kVA.
Why is transformer primary current different from secondary?
Same kVA at different voltages makes different current. Lower secondary voltage means higher secondary current. Total power stays constant (ignoring small losses).
Can I use this to size a breaker?
Calculated current is a start. Final breaker sizing needs continuous load factors, temperature conditions, protection coordination, and code requirements. Check electrical codes and standards.
What does 1.732 mean?
It’s (\sqrt{3}) (square root of 3). It represents the math relationship between line and phase values in balanced three-phase systems. It accounts for how power distributes across three wires.
These formulas work for transformer sizing, generator selection, and load analysis. The math is easy, but you need to know your voltage, phase type, and equipment ratings.
Use calculated values as part of complete electrical design. Include manufacturer data, applicable codes, installation conditions, and safety margins. When unsure, check equipment nameplates and talk to qualified electrical professionals.
Related Calculators
- kW to Amps Calculator
- 3-Phase Power Calculator
- Motor Full Load Current (FLA) Calculator
- IEC Cable Sizing Calculator
- Voltage Drop Calculator
For official motor full-load current values, refer to NEC Article 430 (NFPA 70).
