kVA to kW Calculator

Q: Which voltage should I enter for a three phase system?

Enter the line-to-line voltage, such as 208 V, 400 V, or 480 V. The three phase current formula in this tool uses I = S ÷ (√3 × V), which needs the line-to-line value. 1 If you type a line-to-neutral voltage like 230 V by mistake, the amps will come out too high.

Q: How do I convert motor horsepower to kVA?

Set the direction to kW → kVA , pick hp as the input unit, and type the motor rating. The tool changes hp to kilowatts (1 hp ≈ 0.7457 kW) and then divides by your power factor. 3 One note: nameplate hp is the shaft output. 4 Real motors also lose some power as heat, so divide the hp result by the motor efficiency for the true input power. 3 Induction motor efficiencies generally range from 85% to 97% at full load. 4

Introduction

This kVA to kW calculator changes apparent power (kVA) into real power (kW), or kW back into kVA. Just type your power value, pick a power factor, and get the answer right away.

kVA is the total power delivered to a circuit.¹ kW is the part that does real work, like turning a motor or heating a room.¹ The power factor (PF) links the two. The math is simple: kW = kVA × PF, and kVA = kW ÷ PF.¹

The tool also shows reactive power (kVAR), the phase angle, and a full step-by-step solution. If you add a line voltage and pick single phase or three phase, it will also give you the line current in amps. Charts let you see how your result shifts as the power factor changes.

Use it to size a generator, pick a transformer, check a UPS rating, or plan a panel load. It is a fast helper for electricians, engineers, students, and anyone working with power ratings.

How to use our kVA to kW Calculator

Pick a conversion direction, type in your power value and power factor, and the calculator shows your answer in kW or kVA, plus real power, reactive power, apparent power, phase angle, and line current.

Conversion Direction: Choose kVA → kW to find real power, or kW → kVA to find apparent power. The swap button flips the direction and clears the fields.

System Phase: Select single phase or three phase. This does not change the kW or kVA answer, but it does change the line current result.

Line Voltage: Type your line voltage and pick V or kV. This is optional. Add it if you want the line current in amps, or leave it blank to skip. Long runs may also need a voltage drop check.

Apparent Power (kVA) or Real Power (kW): Enter the value you are converting from and pick its unit. You can choose VA, kVA, or MVA for apparent power, or W, kW, MW, or hp for real power.

Power Factor (PF): Enter a number between 0 and 1. Motors usually sit between 0.8 and 1, and lower when they run at a light load.⁷ Use 1 for pure resistive loads like heaters.⁶

Power Factor Preset: Pick a common load type, like induction motors or LED lighting, and the power factor field fills in for you. Choose Custom to type your own.

Result Unit: Pick the unit for your answer, such as kW, W, MW, hp, kVA, VA, or MVA.

Click Calculate to see the result, the step-by-step math, and the charts. Click Reset to clear everything and start over.

kVA to kW Conversion Explained

Electrical power comes in two forms. kVA (kilovolt-amperes) is apparent power, the total power the wires and the source must carry.¹ kW (kilowatts) is real power, the part that actually does work, like turning a motor or making heat.¹ The link between them is the power factor (PF).¹

The Formulas

kVA to kW: kW = kVA × PF¹
kW to kVA: kVA = kW ÷ PF¹

These formulas are the same for single-phase and three-phase systems.¹ Phase only matters when you want the current in amps.

What Power Factor Means

Power factor is a number from 0 to 1.¹ It tells you how much of the apparent power turns into useful work.¹ A PF of 1 means all of it does.¹ A PF of 0.8 means real power is 80% of the apparent power. The rest of the apparent power is reactive power (kVAR), which bounces back and forth between the source and the circuit.¹ At PF 0.8 the reactive power is 60% of the apparent power, because the three form a right triangle rather than adding up. Reactive behaviour comes from inductance and capacitance, and the impedance calculator shows where it comes from.¹ Motors usually have a power factor between 0.8 and 1, and it drops when a motor runs at a light load.⁷

1.00: heaters, ovens, and other resistive loads.⁶
0.90: LED lighting.
0.85: mixed commercial buildings.
0.80: induction motors.
0.70: big motors running lightly loaded.

The Power Triangle

Real power (P), reactive power (Q), and apparent power (S) form a right triangle:

S² = P² + Q², so Q = √(S² − P²)⁵
The angle between P and S is the phase angle φ, where φ = cos⁻¹(PF)¹

A lower power factor means a bigger angle, and more of the wiring's capacity is taken up by reactive power.⁴

Finding Line Current

If you know the line voltage, you can find the current the circuit will draw:

Single phase: I = S ÷ V¹
Three phase: I = S ÷ (√3 × V)¹

Always size wires, breakers, and fuses using kVA and amps, not kW, because the conductors carry the full apparent power.³

Why This Matters

Generators carry a capacity rating in kVA on their nameplates.¹ Transformers are rated in kVA too.² Many UPS units are as well. Motors, heaters, and appliances are rated in kW. To pick the right generator or transformer, you must convert. For example, a 100 kVA generator at 0.8 PF only supplies 80 kW of real work. If you need 100 kW at 0.8 PF, you need a 125 kVA unit. Guessing wrong here leads to overloaded gear, tripped breakers, and extra cost.

Quick Reference

kVA	PF 0.8 → kW	PF 0.9 → kW	PF 1.0 → kW
10	8	9	10
25	20	22.5	25
50	40	45	50
100	80	90	100
500	400	450	500

Note that kW is never larger than kVA, because power factor is never above 1.

Formulas used

Real Power from Apparent Power (kVA → kW) ¹

P = S \times PF

Apparent Power from Real Power (kW → kVA) ¹

S = \frac{P}{PF}

Reactive Power (Power Triangle) ⁵

Q = \sqrt{S^2 - P^2}

Phase Angle ¹

\varphi = \cos^{-1}(PF) \times \frac{180}{\pi}

Line Current — Three Phase ¹

I = \frac{S}{\sqrt{3} \times V}

Line Current — Single Phase ¹

I = \frac{S}{V}

Unit Conversion of Result

X_{\text{unit}} = \frac{X_{\text{SI}}}{k_{\text{unit}}}

Frequently asked questions

What power factor should I use if I do not know mine?

Check the nameplate on the motor, machine, or panel first. It often lists the PF. If there is no label, use a safe estimate:

1.0 for heaters and other resistive loads⁶
0.8 for motor loads and most job sites
0.85 for mixed shops, stores, and offices
0.9 for LED lighting and modern electronics

A lower guess gives a bigger kVA, which is the safer side when sizing gear. You can also measure it with a power meter or work it out with our PF calculator.

Which voltage should I enter for a three phase system?

Enter the line-to-line voltage, such as 208 V, 400 V, or 480 V. The three phase current formula in this tool uses I = S ÷ (√3 × V), which needs the line-to-line value.¹

If you type a line-to-neutral voltage like 230 V by mistake, the amps will come out too high.

How do I convert motor horsepower to kVA?

Set the direction to kW → kVA, pick hp as the input unit, and type the motor rating. The tool changes hp to kilowatts (1 hp ≈ 0.7457 kW) and then divides by your power factor.³

One note: nameplate hp is the shaft output.⁴ Real motors also lose some power as heat, so divide the hp result by the motor efficiency for the true input power.³ Induction motor efficiencies generally range from 85% to 97% at full load.⁴

What is the difference between kW and kWh?

kW is the rate of power use right now. kWh is how much energy you used over time. A 5 kW load running for 2 hours uses 10 kWh.

This tool works with kW. For energy and cost over time, use the kWh calculator.

Why is my UPS rated 1000 VA but only 700 W?

That is the same kVA to kW conversion at a power factor of 0.7. 1000 VA × 0.7 = 700 W. UPS and generator makers list both numbers because the unit is limited by current (VA) and by real output (W). Never pass either limit.

For a generator, the kW rating depends on the prime mover that turns it and on how much heat the machine can shed, while the current rating depends on its insulation.¹

Does the phase angle tell me if my load is leading or lagging?

No. The tool gives the size of the angle only, using φ = cos⁻¹(PF). Inductive loads such as motors and transformers lag (current behind voltage).¹ Capacitive loads such as big capacitor banks lead.¹ The kW and kVA answers are the same either way.

How can I raise a low power factor?

Common fixes are:

Add capacitors or a power factor correction bank near the motors⁴
Do not run big motors far below full load⁴
Switch old motors for high efficiency ones
Use variable frequency drives, which tend to run at close to unity power factor⁷

Raising PF lowers your kVA and amps for the same kW, so wires and breakers are less loaded.⁶

Does a low power factor raise my power bill?

For most homes, no. Meters bill kWh, which follows real power. Many industrial customers do pay more, because many utilities add a penalty when the power factor falls below 0.90 or 0.95.⁴ Some rate schedules also base demand charges on kVA.⁴ A low PF also forces bigger cables and transformers, which costs money up front.³

What power factor do generator makers assume?

A generator's nameplate gives its capacity in kVA and kW at a specified power factor.¹ Most standby and prime generators are rated at 0.8 PF. So a 100 kVA set gives 80 kW. If your real load has a higher PF, the generator still cannot pass its kVA limit. Check your pick with our generator sizing calculator.

Do I size wires and breakers from kW or kVA?

Use kVA and the amps it gives. Conductors carry the full current, including the reactive part.³ Sizing from kW alone gives too small a wire or breaker at any PF under 1.⁶

Sources

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