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.
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
Free & private
no signup, runs in your browser
Artie has taught physics and electrical theory for over a decade and consulted on real-world electrical design — so every tool here is grounded in both the theory and the field.
University physics lecturer·Consulted on commercial electrical systems·Last reviewed Jul 2026
Ampere Calculator
Convert between amps, kW, kVA and HP for DC and AC single- or three-phase.
A starting point — final size depends on continuous load, derating & terminal ratings.
Enter values to convert.
The power triangle
Next: size the circuit
A starting point — the final size still depends on continuous-load 125%, conductor derating and terminal ratings.
Same apparent power (kVA), different voltage — tap to use
Method — the formula for this case
kVA is apparent power and never uses power factor. kW is real power = kVA × PF. Reactive kVAR = √(kVA² − kW²). Three-phase L-L uses √3 (1.732); L-N uses 3. DC has no reactive power (kVA = kW). HP uses 746 W/HP and efficiency η.
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.
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01
Pick what you know
Choose your starting point — amps, kW, kVA, or horsepower. The tool converts to the rest.
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02
Enter it & the voltage
Type the value and the circuit voltage. You always need the voltage to move between current and power.
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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.
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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
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.
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.
kVA = (A × V) ÷ 1000
A = (kVA × 1000) ÷ V
kW = (PF × A × V) ÷ 1000
A = (kW × 1000) ÷ (V × PF)
Three-phase — multiply by √3 (1.732) using the line-to-line voltage; use 3 instead of √3 for line-to-neutral.
Motors — A = (HP × 746) ÷ (V × η × PF), where η is efficiency; ×√3 for three-phase.
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.
1φ kVA 100 × 240 ÷ 1000 = 24 kVA
1φ kW 24 × 0.8 = 19.2 kW
3φ kVA √3 × 150 × 440 ÷ 1000 = 114.3 kVA
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.
| Voltage | Type | Typical use |
|---|---|---|
| 120 V | AC · 1-phase | Home outlets, lighting |
| 208 V | AC · 3-phase | Commercial (line-to-line) |
| 240 V | AC · 1-phase | Dryers, ranges, EV |
| 400 V | AC · 3-phase | Industrial IEC (L-L) |
| 415 V | AC · 3-phase | Industrial (line-to-line) |
| 440 V | AC · 3-phase | Motors, industrial |
| 480 V | AC · 3-phase | Industrial US (line-to-line) |
| 12–48 V | DC | Battery, solar, telecom |
For three-phase, use the line-to-line voltage with √3; for line-to-neutral, use ×3.
Typical values
Resistive (heaters) 1.0 · induction motors 0.8–0.85 · LED & electronics ~0.9. kVA ignores it; kW depends on it.
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 or 3
Line-to-line uses √3 (≈1.732); line-to-neutral uses 3. The same power draws less current per conductor.
Correction
A low power factor draws more amps for the same kW — and can mean utility penalties. Check power factor →
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
- 01Don't apply PF to kVAkVA is apparent power — amps × volts, full stop. Power factor only affects kW.
- 02Don't size by the wrong powerRate generators, transformers, and UPS by kVA, not kW — kW undersizes them.
- 03Don't use the wrong phaseSingle vs three-phase, and L-L vs L-N, change the √3 factor and your amps.
- 04Don'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 | 1-phase (kVA) | 3-phase (kVA) |
|---|---|---|
| 10 A | 2.4 | 4.2 |
| 20 A | 4.8 | 8.3 |
| 30 A | 7.2 | 12.5 |
| 50 A | 12.0 | 20.8 |
| 100 A | 24.0 | 41.6 |
| 150 A | 36.0 | 62.4 |
| 200 A | 48.0 | 83.1 |
| 400 A | 96.0 | 166.3 |
kVA = amps × volts ÷ 1000 (× √3 for three-phase). For real power in kW, multiply by the power factor.
| Amps | 208 V | 240 V | 400 V | 480 V |
|---|---|---|---|---|
| 50 A | 18.0 kVA | 20.8 kVA | 34.6 kVA | 41.6 kVA |
| 100 A | 36.0 kVA | 41.6 kVA | 69.3 kVA | 83.1 kVA |
| 200 A | 72.1 kVA | 83.1 kVA | 138.6 kVA | 166.3 kVA |
| 400 A | 144.1 kVA | 166.3 kVA | 277.1 kVA | 332.6 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.
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 2023). Results are for planning and estimating. Code adoption, local amendments, and field conditions vary — verify with your AHJ and a licensed electrician before installation.