⚡ kVA Calculator
Calculate apparent power in kilovolt-amperes
Line voltage (for three-phase) or phase voltage (for single-phase)
How to Use This Calculator
Select Phase Type
Choose whether you have a single-phase or three-phase AC system. Most residential systems are single-phase, while industrial and commercial systems are typically three-phase.
Enter Voltage
Input the voltage in Volts. For single-phase, use the phase voltage. For three-phase, use the line-to-line voltage (e.g., 208V, 230V, 400V, 480V).
Enter Current
Input the current in Amperes. For three-phase systems, this is typically the line current.
Calculate
Click the "Calculate kVA" button to get the apparent power in kilovolt-amperes (kVA). This is the total power that the system must supply.
Formula
Single Phase
kVA = (V × I) / 1000
Three Phase
kVA = (√3 × V × I) / 1000
Where:
- kVA = Apparent Power (kilovolt-amperes)
- V = Voltage (Volts, V)
- I = Current (Amperes, A)
- √3 ≈ 1.732 (for three-phase)
Example Calculation:
For a three-phase system with V = 400V, I = 50A:
kVA = (√3 × 400 × 50) / 1000
kVA = (1.732 × 400 × 50) / 1000
kVA = 34.64 kVA
Note: kVA is apparent power, which includes both real power (kW) and reactive power (kVAR). For real power: kW = kVA × power factor.
About kVA Calculator
The kVA Calculator determines the apparent power in kilovolt-amperes (kVA) for AC electrical systems. Apparent power is the total power that must be supplied to a circuit, including both real power (kW) that does work and reactive power (kVAR) required by inductive or capacitive loads. kVA is crucial for sizing generators, transformers, and electrical distribution equipment.
When to Use This Calculator
- Electrical Design: Size generators, transformers, and switchgear
- Power System Planning: Determine total apparent power requirements
- Equipment Selection: Select appropriate electrical equipment ratings
- Load Calculations: Calculate total electrical load in facilities
- Generator Sizing: Size backup generators for building loads
Why Use Our Calculator?
- ✅ Dual Phase Support: Handles both single-phase and three-phase calculations
- ✅ Quick Calculation: Instantly determine apparent power from voltage and current
- ✅ Equipment Sizing: Essential for proper electrical equipment selection
- ✅ Free Tool: No registration or payment required
- ✅ Educational: Learn about apparent power and electrical system design
Common Applications
Transformer Sizing: Calculate the kVA rating needed for transformers based on load requirements. Transformers are rated in kVA because they must handle both real and reactive power. Proper sizing ensures transformers can supply the total apparent power needed without overload.
Generator Selection: Determine generator capacity in kVA for backup power systems. Generators must be sized to handle the total apparent power (kVA) of all connected loads, not just real power (kW), especially when motors and other inductive loads are present.
Electrical Service Sizing: Calculate total kVA requirements for building electrical services. Utility companies often bill based on kVA demand because they must supply the total apparent power, including reactive power that doesn't do useful work but still requires capacity.
Tips for Best Results
- kVA represents apparent power (total power), while kW represents real power (useful work)
- For three-phase systems, use line-to-line voltage and line current
- kW = kVA × power factor (typically 0.8-0.95 for most loads)
- Always size equipment based on kVA, not just kW, to account for reactive power
- Add 20-25% safety margin when sizing equipment for future growth
Frequently Asked Questions
What is kVA?
kVA (kilovolt-ampere) is a unit of apparent power in AC electrical systems. It represents the total power that must be supplied, including both real power (kW) that does useful work and reactive power (kVAR) required by inductive or capacitive loads. kVA = √(kW² + kVAR²).
What's the difference between kVA and kW?
kW (kilowatts) is real power - the power that actually does useful work. kVA (kilovolt-amperes) is apparent power - the total power that must be supplied. The relationship is: kW = kVA × power factor. For example, a 100 kVA load with 0.85 power factor consumes 85 kW of real power.
Why is √3 used for three-phase calculations?
In three-phase systems, the three phases are 120° out of phase. The √3 factor (approximately 1.732) accounts for the phase relationship between line voltage and phase voltage. Line voltage = √3 × phase voltage in balanced three-phase systems.
Should I size equipment based on kVA or kW?
Size equipment (generators, transformers, switchgear) based on kVA because they must handle the total apparent power, including reactive power. While kW tells you real power consumption, kVA tells you the total power capacity needed from the source.
What is power factor and how does it relate to kVA?
Power factor (PF) is the ratio of real power (kW) to apparent power (kVA): PF = kW/kVA. It ranges from 0 to 1. A low power factor means more reactive power is needed. Utilities often charge penalties for low power factor because it wastes capacity. Power factor correction can reduce kVA requirements.
How do I convert kVA to kW?
Multiply kVA by the power factor: kW = kVA × PF. For example, 50 kVA at 0.9 power factor = 45 kW. Power factor is typically 0.8-0.95 for most loads. Motors and other inductive loads have lower power factors (0.6-0.8), while resistive loads (heaters) have power factor near 1.0.