Air Density Calculator
Calculate air density from pressure, temperature, and humidity using the ideal gas law. Includes altitude reference table and moist air corrections.
kVA Calculator
Calculate kVA, kW, kVAR, current, and power factor for single-phase and three-phase electrical systems with power triangle visualization.
Apparent Power (kVA)⧉
100.00 kVA
S = V × I / 1000 (single) or S = √3 × V × I / 1000 (three-phase)
Real Power (kW)⧉
85.00 kW
P = S × PF — actual useful power
Reactive Power (kVAR)⧉
52.68 kVAR
Q = S × sin(φ) — power stored/returned by reactive loads
Current⧉
120.28 A
Per phase — three-phase
Power Factor⧉
0.850
Phase angle = 31.8°
Phase Angle⧉
31.8°
φ = arccos(PF)
Power Triangle
kW
kVAR
kVA
| PF | kW | kVAR |
|---|---|---|
| 0.8 | 80.0 | 60.0 |
| 0.85 | 85.0 | 52.7 |
| 0.9 | 90.0 | 43.6 |
| 0.95 | 95.0 | 31.2 |
| 1 | 100.0 | 0.0 |
Common Transformer Sizes
| kVA | Typical Use | Voltage |
|---|---|---|
| 15 | Small residential | 240/120 |
| 75 | Small commercial | 480/208 |
| 150 | Medium commercial | 480/208 |
| 500 | Large commercial | 480/208 |
| 1000 | Industrial | 4160/480 |
| 2500 | Utility substation | 13200/480 |
Planning notes, formulas, and examples
About the kVA Calculator
kVA (kilovolt-amperes) is the unit of apparent power in electrical systems — the total power flowing in a circuit including both useful real power (kW) and reactive power (kVAR). Understanding the relationship between these quantities is essential for sizing transformers, generators, UPS systems, and electrical panels.
The power factor (PF) connects real and apparent power: kW = kVA × PF. A power factor of 1 means all power is useful; lower power factors indicate reactive loads (motors, fluorescent ballasts) that draw extra current without doing useful work. Utility companies often penalize low power factor because it requires oversized infrastructure.
This kVA Calculator handles both calculation directions — from kVA to kW and current, or from voltage and current to kVA and kW — for single-phase and three-phase systems. It computes reactive power, phase angle, and provides a power factor sensitivity table and power triangle visualization. Preset buttons cover common scenarios from residential panels to industrial motors.
When This Page Helps
Use this calculator when you need to move quickly between kVA, kW, current, and power factor without rebuilding the power triangle by hand.
It is especially useful for transformer sizing, generator checks, UPS planning, and comparing how the same load behaves at different power factors. It also keeps apparent power, real power, and reactive power together so the electrical load is easier to compare across scenarios.
How to Use the Inputs
- Select the calculation mode: kVA → kW or V & I → kVA.
- Choose single-phase or three-phase system.
- Enter the system voltage.
- Enter the kVA rating or the current depending on mode.
- Enter the power factor (0.8 is typical for motors).
- Review kVA, kW, kVAR, current, and phase angle.
- Use the power factor table to see the effect of PF on real power.
Formula used
Single Phase: S = V × I / 1000 (kVA)
Three Phase: S = √3 × V × I / 1000 (kVA)
Real Power: P = S × PF (kW)
Reactive Power: Q = S × sin(arccos(PF)) (kVAR)
Power Factor: PF = cos(φ)Example Calculation
Result: kW = 85, kVAR = 52.7, I = 120.3 A per phase
A 100 kVA three-phase transformer at 480 V and 0.85 PF delivers 85 kW of real power while handling 52.7 kVAR of reactive power.
Tips & Best Practices
- Use the correct phase model first: single-phase and three-phase formulas are not interchangeable.
- For most three-phase service calculations, enter line-to-line voltage unless your source data explicitly lists phase voltage.
- Size generators, transformers, and UPS systems by kVA, then verify that the expected kW still works at the actual power factor.
- Check motor starting current separately from steady-state current because inrush can dominate equipment sizing.
Practical Guidance
Start with a clean load list and convert each item to a common basis before you add them together. Resistive heaters and incandescent lighting often sit near unity power factor, while motors, welders, compressors, and many electronic loads can demand noticeably more apparent power than their kW rating suggests.
Common Pitfalls
The most common errors are using the wrong voltage definition in a three-phase system, mixing kW and kVA as if they were interchangeable, and ignoring poor power factor when sizing equipment. If motors are involved, also check locked-rotor or startup demand because the transient current can be much higher than the running value.
Sources & Methodology
Last updated:
Frequently Asked Questions
kVA is apparent power (total), kW is real power (useful work). They differ when the power factor is less than 1 due to reactive loads.
Transformer losses depend on current (which determines conductor heating), not on whether the load is resistive or reactive. kVA measures the total current demand.
Above 0.9 is generally acceptable. Utilities may charge penalties for PF below 0.85. Power factor correction capacitors can improve PF.
Sum the kVA ratings of all connected loads (or calculate from kW ÷ PF). Add 20–25% margin for starting surges.
kVAR is the power that oscillates between source and load without doing work. It is required by inductive loads (motors, transformers) to maintain magnetic fields.
Single-phase: S = V×I. Three-phase: S = √3×V×I (using line-to-line voltage). The √3 factor accounts for the three phases.
More in this topic
Angle of Repose Calculator
Calculate the angle of repose for granular materials. Find pile height, volume, slope ratio, and stability from friction coefficient and density.
Angle of Twist Calculator
Calculate angle of twist, shear stress, and torsional stiffness for solid or hollow shafts under torque. Compare materials side by side.