Formula Used
For line to line voltage, kVA = √3 × V × I ÷ 1000.
For line to neutral voltage, kVA = 3 × V × I ÷ 1000.
Current = kVA × 1000 ÷ voltage factor ÷ V.
Voltage = kVA × 1000 ÷ voltage factor ÷ I.
kW = kVA × power factor. kVAR = kVA × √(1 − power factor²).
Motor input kVA = HP × 0.746 ÷ efficiency ÷ power factor.
Demand adjusted kVA = base kVA × demand factor. Recommended kVA = demand adjusted kVA × (1 + safety margin).
How to Use This Calculator
Select the calculation type first. Use voltage and current when you have field measurements. Use known kVA to solve current or voltage. Use kW or horsepower when planning motors or real load data.
Choose line to line voltage for most three phase panel and equipment ratings. Choose line to neutral only when that is the measured phase voltage. Enter power factor as a decimal, such as 0.85.
Add demand factor, load factor, and margin when checking practical capacity. Press Calculate to show results above the form. Use the CSV and PDF buttons to save the same calculation.
Example Data Table
| Load |
Voltage |
Current |
Power Factor |
Base kVA |
Use Case |
| Small workshop panel |
400 V |
90 A |
0.86 |
62.35 kVA |
Panel capacity check |
| Motor control center |
415 V |
150 A |
0.88 |
107.82 kVA |
Transformer review |
| Generator load bank |
480 V |
220 A |
0.80 |
182.90 kVA |
Generator sizing |
Why Three Phase kVA Matters
Three phase systems move large power with smooth delivery. kVA shows apparent power. It combines voltage and current before power factor is applied. This value helps size transformers, generators, panels, breakers, cables, and backup systems. A good estimate reduces overload risk. It also avoids buying equipment that is much larger than needed.
Balanced Load Basics
This calculator assumes a balanced three phase load unless you enter demand and load factors. Balanced loads share current evenly across each phase. For line to line voltage, the standard formula uses the square root of three. For line to neutral voltage, the formula uses three. Both methods reach the same result when the voltage type is correct. Always select the voltage that matches your measurement point.
Using Power Factor
Power factor links apparent power to real power. A motor, compressor, or transformer may draw extra reactive current. That current raises kVA without doing useful work. The tool estimates kW from kVA and power factor. It can also estimate input kVA when output power and efficiency are known. This is useful when checking motors, drives, and generators.
Demand and Safety Review
Real sites rarely run every load at full rating. Demand factor reduces the connected estimate. Load factor can show the average operating share. The calculator reports base kVA, adjusted kVA, kW, current, and margin. Use the margin field to add spare capacity. Many planners use spare capacity for future circuits, starting surge, heat, and measurement error.
Practical Notes
Use nameplate voltage and current when quick data is needed. Use measured values for a better field estimate. Keep units consistent. Enter amps, volts, percent values, and known output power carefully. The result is an engineering aid, not a final protection design. Check local codes and equipment manuals before choosing conductors or breakers.
Export and Documentation
The export buttons help keep a project record. CSV works well for spreadsheets. PDF is useful for quotes, reviews, and job files. Save the result with the input values, because later checks need the same assumptions. Record the voltage source, power factor, efficiency, and margin. Small notes can prevent confusion when another person reviews the calculation. This also supports cleaner equipment discussions with contractors later.
FAQs
What is kVA in a three phase circuit?
kVA is apparent power. It combines voltage and current before power factor is applied. It is often used for transformer, generator, and distribution equipment sizing.
Should I use line to line or line to neutral voltage?
Use line to line voltage for most three phase equipment ratings. Use line to neutral only when your measurement is from one phase to neutral.
Why does the formula use √3?
The square root of three appears because three phase line values are separated by 120 electrical degrees. It converts line voltage and line current into total apparent power.
How is current calculated from kVA?
For line to line voltage, current equals kVA times 1000 divided by √3 and voltage. The calculator also supports line to neutral voltage.
Does power factor change kVA?
Power factor does not change apparent power from measured volts and amps. It changes the real power estimate, because kW equals kVA multiplied by power factor.
Can this calculator size a generator?
It can support early generator sizing. Add demand factor and margin. Also check starting current, harmonic loads, site rules, and manufacturer guidance.
What is demand adjusted kVA?
Demand adjusted kVA is base kVA multiplied by the demand factor. It estimates the portion of connected load expected to run together.
Is this a final electrical design tool?
No. It is a planning calculator. Final conductor, breaker, transformer, and generator choices should follow local codes and qualified electrical design review.