FORMULA
Three-Phase kVA Formula
kVA = (√3 × Volts × Amps) ÷ 1,000
Line-to-line voltage × line current × 1.732, divided by 1,000.
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kVA Explained
What a kVA Calculator Does
A kVA calculator performs one essential job: it converts between the units used to describe electrical power. Three units matter in every sizing decision.
kW
Real Power
The real, usable power your equipment consumes. Motors, heaters, and lighting all use it.
kVA
Apparent Power
The total power capacity the generator, transformer, or UPS must supply. This is the rating stamped on the equipment.
Amps
Current
The current flowing at your system voltage, which determines cable size and breaker rating.
Power Factor & Phase Determine the Relationship
The relationship between kW, kVA, and amps depends on two things: the power factor of your load and whether the system is single-phase or three-phase. A good calculator handles all of it in one step.
More Than a Simple Converter
What Makes This Tool Different
01
Convert in Both Directions
kW to kVA, kVA to amps, amps to kVA, and volts — all on one page. No need for multiple tools.
02
Dedicated Generator Sizing Mode
Enter your load in kW or amps and it returns the kVA generator you need, mapped to a real Huali model.
03
Global Standards
Supports single-phase and three-phase at 50 Hz and 60 Hz — so the result is valid in your country, not just the US.
04
From Conversion to Quote
Every result ends in a free factory-direct quote, so you move from conversion to price in one step.
kVA Converter
kVA Calculator 3 Phase: kW & Amps Converter
Convert kW, kVA, amps, volts, and power factor instantly. Works for single-phase and three-phase at 50 Hz or 60 Hz. Size your generator correctly, then request a quote.
Convert Between kVA, kW, Amps & Volts
Enter any two known values. The calculator fills in the rest using the standard power formulas.
Typical industrial: 0.8. Motors: 0.7–0.9. Resistive loads: 1.0.
Size Your Generator from kW Load
Enter your total connected load. The calculator returns the required kVA, recommended generator class, and headroom margin.
Line-to-line for three-phase.
0.8 is the industrial standard. Adjust for your load type.
kVA Reference Table
kVA to Amps Reference Table (Three-Phase)
This table gives the current for common kVA sizes at the three most common three-phase voltages. Use it to sanity-check a calculation, size a breaker, or select cable before you finalize. For any voltage or kVA outside this table, run it through the kVA to amps calculator above.
| kVA | Amps @ 230 V | Amps @ 400 V | Amps @ 480 V |
|---|---|---|---|
| 10 kVA | 25 A | 14 A | 12 A |
| 20 kVA | 50 A | 29 A | 24 A |
| 50 kVA | 126 A | 72 A | 60 A |
| 100 kVA | 251 A | 144 A | 120 A |
| 150 kVA | 377 A | 217 A | 180 A |
| 200 kVA | 502 A | 289 A | 241 A |
| 250 kVA | 628 A | 361 A | 301 A |
| 300 kVA | 753 A | 433 A | 361 A |
| 500 kVA | 1,255 A | 722 A | 601 A |
Values are rounded for line-to-line voltage at 0.8 power factor reference. Single-phase current is roughly 73% higher per kVA at the same voltage — another reason to verify with the calculator before ordering cables.
This table covers the sizes in our standard diesel generator range from 8 kVA to 4,000 kVA. If your project needs a size you do not see here, we offer OEM/ODM customization across the full range.
This table covers the sizes in our standard diesel generator range from 8 kVA to 4,000 kVA. If your project needs a size you do not see here, we offer OEM/ODM customization across the full range.
Why Generators Are Rated in kVA
Manufacturers rate generators in kVA because the alternator's limit is about current, not watts. kVA = volts × amps captures that physical limit directly. The kW a generator delivers depends on your load's power factor, so the honest rating is the kVA value, with kW quoted at a reference power factor (usually 0.8). Compare generators on kVA first — it is the true capacity.
Three-Phase Power
How to Calculate kVA for Three-Phase Power
The 3-phase kVA formula is the foundation of every sizing decision. It uses line-to-line voltage and the square root of 3 (√3 ≈ 1.732):
WHY √3
The √3 Factor
Unique to three-phase systems. Comes from the geometry of three phases spaced 120° apart. Omit it and you get only 58% of the true kVA — a 42% under-estimate that undersizes your generator.
EXAMPLE
Worked Example
A 400 V three-phase supply carrying 200 A per phase:
kVA = (1.732 × 400 × 200) ÷ 1,000 = 138.6 kVA
SINGLE-PHASE
Single-Phase Formula
No √3 factor:
kVA = (Volts × Amps) ÷ 1,000
For comparison — single-phase current is roughly 73% higher per kVA at the same voltage.
REVERSE
Amps from kVA
Three-phase:
Amps = (kVA × 1,000) ÷ (√3 × Volts)
Single-phase:
Amps = (kVA × 1,000) ÷ Volts
Key Takeaway
Always Apply √3 for Three-Phase
The √3 factor is the most commonly skipped step in power calculations. Omitting it under-estimates power by about 42% — a direct path to an undersized generator. Use the converter above to run your own numbers in either direction.
Why Generators Oversize
Power Factor and Motor Starting: Why Generators Oversize
Two forces push industrial generators to sizes that look "too big" on paper: power factor and motor starting.
01
Power Factor Determines kVA Need
A site full of motors and pumps runs at a lower power factor than one full of heating and lighting. At 0.8 PF you need 25% more kVA than your kW total; at 0.7 PF you need more than 40% more.
02
Reactive Power Is Real
The extra kVA is not waste — it is the reactive power your motors and inductive loads genuinely require to magnetize their windings.
03
Motor Starting Sets the Peak
The locked-rotor current a motor draws in its first seconds is far above its running current. The peak, not the average, determines the generator size.
04
Direct-on-Line (DOL)
6–8× full-load current — the largest generator required. Use when no other starting method is available.
05
Star-Delta / Soft Starter
2–3× full-load current. A soft starter or star-delta reduces the starting surge roughly in half compared to DOL, often allowing a smaller generator.
06
VFD & Stagger-Start
A VFD draws 1–1.5× full-load current — the smallest generator required. Where a site can stagger-start its largest motors, the generator can be smaller still.
Common Errors
5 Common kVA Mistakes to Avoid
We see these five errors repeatedly in real-world projects. Avoid all of them and your generator sizing will be defensible from the start.
Forgetting the √3 Factor
Omitting 1.732 in a three-phase calculation under-estimates power by about 42%. Always apply it for three-phase, and never for single-phase.
Using Line-to-Neutral Voltage
Three-phase kVA uses line-to-line voltage. Mixing the two gives a wrong result by a factor of √3.
Treating kW and kVA as Identical
Always divide by the power factor. A 100 kW load is not a 100 kVA generator — at 0.8 PF it is roughly 125 kVA.
Ignoring Motor Starting
A generator that carries your running load all day can still trip the instant a compressor's locked-rotor current hits it. Size for the largest start.
Sizing to 100% of Rating
Running a generator at full load leaves no margin for surge, altitude, temperature, or growth. Always use the 20–25% headroom.
Not sure your calculation is right? Our engineers will review your load list and confirm the kVA before you spend anything. Talk to our engineers.
Let's talk
Get a Factory-Direct Quote
Our engineers will review your calculated kVA, confirm the specification, and deliver a factory-direct price — no obligation, no hidden fees. Every quote includes the generator, automatic transfer switch, and soundproofed enclosure for a complete commercial solution.
Frequently Ask Questions
Q: How many amps is a 100 kVA three-phase supply?
A: At 400 V line-to-line, a 100 kVA three-phase supply carries about 144 A per phase (100 × 1,000 ÷ (1.732 × 400)). At 480 V it is about 120 A; at 230 V it is about 251 A. The calculator returns the exact value for your voltage.
Q: How do I convert kW to kVA?
A: Divide the kW by the power factor: kVA = kW ÷ PF. At the standard 0.8 power factor, a 100 kW load needs 125 kVA. Our kW to kVA calculator above does this instantly.
Q: What is the formula for three-phase kVA?
A: kVA = (√3 × Volts × Amps) ÷ 1,000, using line-to-line voltage and line current. √3 is approximately 1.732. This is the formula used throughout this page and by every manufacturer’s sizing tool.
Q: Is kVA the same as kW?
A: No. kVA is apparent power and kW is real power. They are linked by the power factor: kW = kVA × PF. A generator rated 100 kVA at 0.8 PF delivers 80 kW of usable power.
Q: Why are generators rated in kVA and not kW?
A: Because the alternator’s physical limit is current at a fixed voltage, which is exactly what kVA measures. The real kW a generator delivers depends on the power factor of your load, so the fixed rating is quoted in kVA.
Q: How many amps does a 125 kVA generator provide?
A: A 125 kVA generator at 400 V three-phase provides about 180 A per phase (125 × 1,000 ÷ (1.732 × 400)). At 230 V three-phase it is about 314 A per phase.
Q: What size generator do I need for a 45 kW load?
A: At 0.8 power factor, 45 kW = 56 kVA. With a 25% safety margin you reach about 70 kVA, so a 75 kVA (60 kW) diesel genset is the right size. Our generator sizing calculator confirms this with your full load list.
Q: Do you supply generators in my required kVA?
A: Yes. Our range spans 8 kVA to 4,000 kVA in standard sizes, at 50 Hz or 60 Hz, single- or three-phase. If your calculated size falls between standard ratings, we offer OEM/ODM customization to match your exact specification.