Amps · power · current

Ampere
Calculator

Convert between amps, kilowatts, and kilovolt-amps for any circuit. The key: kVA is the total power your supply carries; kW is the useful part — and kW = kVA × PF. Works for DC, single- and three-phase, plus horsepower.

An ampere calculator built for pros — clear enough for anyone.

Apparent vs real power live
FIG. 1 — APPARENT vs REAL POWER 100 A × 240 V · single-phase APPARENT POWER 24 kVA reactive 19.2 kW real power 24 kVA × PF 0.8 power factor = the share of apparent power that does real work
Try it · power factor →

Same amps and volts means the same 24 kVA — but a lower power factor means less of it is real, useful kW. The gap is reactive power the supply still has to carry.

Amps ↔ kW ↔ kVA

convert in any direction

DC · 1φ · 3φ · HP

every system & motor

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Dean Bailey
Written & reviewed by
Dean Bailey — Master Electrician, Texas · 35+ years' experience
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Ampere Calculator

Convert between amps, kW, kVA and HP for DC and AC single- or three-phase.

—— S = V × I
A

Have watts or kW to convert straight to amps? Use the Watt-to-Amp calculator →

Power factor applies to real power (kW / HP) only — never to kVA. Resistive = 1.0; motors ~0.8.

—
—

Enter values to convert.

The power triangle

Current
—
at the entered voltage
Apparent power
—
what the supply must carry
Current
—
A
Real power
—
kW
Apparent
—
kVA
Reactive
—
kVAR
Power factor
—
used
Voltage
—
V

Next: size the circuit

A starting point — the final size still depends on continuous-load 125%, conductor derating and terminal ratings.

For planning and conversion. For breaker and conductor sizing apply the relevant code rules (continuous-load 125%, derating, terminal ratings; motors per Art. 430). Three-phase assumes a balanced system. Verify against the adopted code and consult a licensed electrician.

How to use it

How to use the ampere calculator

Tell it what you know — amps, kilowatts, kilovolt-amps, or horsepower — then add the voltage and phase. It converts between all of them instantly, keeping apparent (kVA) and real (kW) power straight, and points you to sizing the wire and breaker.

  1. 01

    Pick what you know

    Choose your starting point — amps, kW, kVA, or horsepower. The tool converts to the rest.

  2. 02

    Enter it & the voltage

    Type the value and the circuit voltage. You always need the voltage to move between current and power.

  3. 03

    Set the phase & power factor

    Pick DC, single-, or three-phase. For kW and motors, add the power factor — kVA doesn't need it.

  4. 04

    Read the conversions & size it

    Get amps, kW, and kVA at once — then size the wire, breaker, or convert watts in a tap.

The core idea

kVA, kW, and the power factor

One current, three ways to measure the power.

Amps and volts set the apparent power (kVA) — the total your supply must carry. The power factor then splits it: the real power (kW) that does work, and the reactive power (kVAR) that doesn't. kW = kVA × PF.

The power triangle — power factor is the angle

θ REAL 19.2 kW REACTIVE 14.4 kVAR APPARENT 24 kVA PF = cos θ = 0.8
Real powerkW = kVA × PF
ApparentkVA = kW ÷ PF
ReactivekVAR = √(kVA²−kW²)
Power factorPF = kW ÷ kVA

Amps set the apparent power — kVA = V × I ÷ 1000. The power factor then decides how much of it is real, working kW.

For three-phase, multiply by √3. Use the line-to-line voltage: kVA = √3 × V × I ÷ 1000 (√3 ≈ 1.732). The same power spread across three conductors draws less current per phase than single-phase.

The rule

kW = kVA × PF — kVA = (√3 × V × I) ÷ 1000 for three-phase

The method

The ampere formulas

Two families of formula, split by power factor. Apparent power (kVA) comes straight from amps and volts — no power factor. Real power (kW) is the apparent power times the power factor. For three-phase, multiply by √3.

Apparent · kVAno power factor
amps → kVA

kVA = (A × V) ÷ 1000

kVA → amps

A = (kVA × 1000) ÷ V

Real · kWpower factor applies
amps → kW

kW = (PF × A × V) ÷ 1000

kW → amps

A = (kW × 1000) ÷ (V × PF)

the bridge kW = kVA × PF
× √3

Three-phase — multiply by √3 (1.732) using the line-to-line voltage; use 3 instead of √3 for line-to-neutral.

HP

Motors — A = (HP × 746) ÷ (V × η × PF), where η is efficiency; ×√3 for three-phase.

Worked 100 A × 240 V = 24 kVA · × PF 0.8 = 19.2 kW single-phase
Remember

kVA never uses power factor · kW = kVA × PF · apparent is what the supply carries, real is what does work

Worked example

Convert 100 amps to kVA and kW

At 240 V single-phase, 100 amps is 24 kVA of apparent power — the total the supply carries. At a power factor of 0.8, 19.2 kW of that is real, working power. The rest is reactive.

Convert 100 A240 Vsingle-phasekVA = A × V ÷ 1000
100 A · 240 V · 1-phase · PF 0.8 24 kVA apparent19.2 kW real the answer
real kW is 80% of the apparent kVA — that's the power factor
150 A · 440 V · 3-phase · PF 0.85 114.3 kVA apparent97.2 kW real ×√3 for three-phase
real kW is 85% of the apparent kVA

1φ kVA 100 × 240 ÷ 1000 = 24 kVA

1φ kW 24 × 0.8 = 19.2 kW

3φ kVA √3 × 150 × 440 ÷ 1000 = 114.3 kVA

the answer

100 A at 240 V is 24 kVA apparent — the total the supply must carry — of which 19.2 kW is real, working power at PF 0.8. Size generators and transformers by the kVA; the kW is what does the work and shows on the bill.

The reference

kVA vs kW & the fine print

The one distinction that matters: apparent power (kVA) is the total your supply must carry — it sizes generators, transformers, and UPS units. Real power (kW) is the useful part that does work and shows on the bill. Power factor connects them.

★ 480 V — common industrial three-phase
Common voltages, whether single- or three-phase or DC, and their typical use
VoltageTypeTypical use
120 VAC · 1-phaseHome outlets, lighting
208 VAC · 3-phaseCommercial (line-to-line)
240 VAC · 1-phaseDryers, ranges, EV
400 VAC · 3-phaseIndustrial IEC (L-L)
415 VAC · 3-phaseIndustrial (line-to-line)
440 VAC · 3-phaseMotors, industrial
480 VAC · 3-phaseIndustrial US (line-to-line)
12–48 VDCBattery, solar, telecom

For three-phase, use the line-to-line voltage with √3; for line-to-neutral, use ×3.

POWER FACTOR

Typical values

Resistive (heaters) 1.0 · induction motors 0.8–0.85 · LED & electronics ~0.9. kVA ignores it; kW depends on it.

FLA

Motor sizing

Computed motor amps are an estimate. NEC uses table full-load values (430.248 / 430.250) for wire & breaker, at 125%. Size the breaker →

3-PHASE

√3 or 3

Line-to-line uses √3 (≈1.732); line-to-neutral uses 3. The same power draws less current per conductor.

LOW PF

Correction

A low power factor draws more amps for the same kW — and can mean utility penalties. Check power factor →

WATTS

Have watts?

Converting plain watts (W) or kW straight to amps? Use the Watt-to-Amp calculator →

What affects it

What moves the numbers — and the common mistakes

The conversion shifts with three things — the voltage, the power factor (which changes kW but never kVA), and the phase. The mistakes cluster there too: applying power factor to kVA, or mixing up apparent and real power.

What moves the numbers

the levers

  • VoltageInverse with current — the same power draws fewer amps at higher voltage. It scales the kVA directly.
  • Power factorChanges the real kW only — kVA is fixed by amps and volts. A lower PF means less useful kW.
  • PhaseThree-phase divides by √3, so the same power draws less current per conductor than single-phase.
  • Efficiency (motors)HP is output — input amps use efficiency and PF. A less efficient motor draws more current.

Common conversion mistakes

what trips people up

  1. 01
    Don't apply PF to kVAkVA is apparent power — amps × volts, full stop. Power factor only affects kW.
  2. 02
    Don't size by the wrong powerRate generators, transformers, and UPS by kVA, not kW — kW undersizes them.
  3. 03
    Don't use the wrong phaseSingle vs three-phase, and L-L vs L-N, change the √3 factor and your amps.
  4. 04
    Don't forget motor efficiencyHP is output; input amps use efficiency and PF, or they come out too low.

The rule

kVA is fixed — power factor only moves the kW

Amps × volts (× √3 for three-phase) sets the apparent power, full stop. The power factor then decides how much of it is real, working kW — it never touches the kVA.

Size a generator by the wrong number and you'll undersize it. A 100 kVA load at PF 0.8 is only 80 kW of real power — but the generator still has to be rated for the full 100 kVA, reactive part included.

Quick chart

Amps to kVA, at a glance

Pick amps, voltage, and phase to get the apparent power (kVA) — or switch to real power (kW) or reverse it. For the common one — 100 amps at 240 V single-phase — that's 24 kVA.

kVA is apparent power — it doesn't use power factor. Switch to kW to apply it.

Apparent power

24.0 kVA

100 A × 240 V ÷ 1000

Amps → kVA at 240 V

Amps converted to apparent power kVA at 240 volts, single-phase and three-phase
Amps1-phase (kVA)3-phase (kVA)
10 A2.44.2
20 A4.88.3
30 A7.212.5
50 A12.020.8
100 A24.041.6
150 A36.062.4
200 A48.083.1
400 A96.0166.3

kVA = amps × volts ÷ 1000 (× √3 for three-phase). For real power in kW, multiply by the power factor.

Amps to kVA three-phase conversion at 208 V, 240 V, 400 V, and 480 V
Amps208 V240 V400 V480 V
50 A18.0 kVA20.8 kVA34.6 kVA41.6 kVA
100 A36.0 kVA41.6 kVA69.3 kVA83.1 kVA
200 A72.1 kVA83.1 kVA138.6 kVA166.3 kVA
400 A144.1 kVA166.3 kVA277.1 kVA332.6 kVA
How do I convert amps to kVA?

Multiply amps by volts and divide by 1,000: kVA = (A × V) ÷ 1,000. For three-phase, multiply by √3 (1.732). Apparent power (kVA) doesn't use power factor — that's only for kW.

What's the difference between kVA and kW?

kVA is apparent power — the total your supply must carry. kW is real power — the useful part that does work and shows on the bill. They're equal only at power factor 1.0; otherwise kW = kVA × PF.

How do I convert amps to kW?

kW = (PF × A × V) ÷ 1,000 for single-phase, or × √3 for three-phase. Unlike kVA, kW needs the power factor — 1.0 for resistive loads, about 0.8 for motors.

How do I convert kVA to amps?

Reverse the formula: A = (kVA × 1,000) ÷ V for single-phase, or ÷ (√3 × V) for three-phase. A 100 kVA three-phase load at 400 V draws about 144 A.

Do I need power factor to find kVA?

No. kVA is apparent power — just amps × volts (× √3 for three-phase). Power factor only comes in when you convert to real power (kW). Applying it to kVA is the most common mistake.

How do I convert horsepower to amps?

A = (HP × 746) ÷ (V × efficiency × PF), and × √3 for three-phase. HP is the motor's output, so efficiency and power factor account for the extra current the motor actually draws.

What's the three-phase formula?

For three-phase line-to-line: kVA = (√3 × V × I) ÷ 1,000, where √3 ≈ 1.732. If your voltage is measured line-to-neutral, use 3 instead of √3.

Why does three-phase use √3?

Three-phase power is delivered across three conductors offset by 120°. The √3 (≈1.732) factor accounts for how those phases combine, so the same power draws less current per conductor than single-phase.

Keep going

Related electrical calculators

You've got the amps — now put them to work. These pick up from there: convert watts, size the wire, and protect the circuit, all on the same NEC-based engine.

01 Watt to Amp Calculator Have watts or kW instead? Convert straight to amps for DC, single-, or three-phase. Open 02 Wire Size Calculator Size the conductor for the current you found — the smallest safe gauge for the load and run. Open 03 Circuit Breaker Size Protect the circuit — the right breaker for that current, with the 125% continuous-load rule applied. Open
Browse all electrical calculators

How we keep this accurate

Conversions use the standard relationships — kVA = V × I ÷ 1000, kW = kVA × PF, × √3 for three-phase. Sizing tools follow the National Electrical Code (NEC 2026). Results are for planning and estimating. Code adoption, local amendments, and field conditions vary — verify with your AHJ and a licensed electrician before installation.

Last updated September 2026 · Verified against the National Electrical Code (NEC 2026).