Convert kVA to amps for single-phase and three-phase systems. Includes power factor, wire sizing, breaker selection, and power triangle.
Converting kVA (kilovolt-amperes) to amperes is one of the most common calculations in electrical engineering and power system design. Whether you are sizing a transformer, selecting circuit breakers, choosing wire gauges, or specifying generator capacity, you need to know the actual current draw in amperes to make safe and code-compliant decisions.
The relationship between kVA and amps depends on whether you have a single-phase or three-phase system. For single-phase circuits, the current equals the apparent power divided by the voltage. For three-phase systems, the voltage is multiplied by the square root of 3 (approximately 1.732), which accounts for the phase relationship between the three conductors.
This calculator handles both single-phase and three-phase conversions, incorporates power factor and efficiency for real-world accuracy, and provides practical guidance including NEC-compliant wire sizing and breaker recommendations. The power triangle visualization clearly shows the relationship between real power (kW), reactive power (kVAR), and apparent power (kVA).
Electrical equipment ratings are commonly given in kVA, but practical installation decisions — wire size, breaker rating, conduit fill, and panel capacity — all depend on the actual current in amperes. This calculator bridges that gap, converting apparent power to current while accounting for real-world factors like power factor and system efficiency.
The built-in wire sizing and breaker recommendations based on NEC standards help you move directly from a load calculation to a material specification, saving time and reducing the risk of undersizing critical electrical components.
kVA to Amps Conversion: • Single Phase: I = (kVA × 1000) / V • Three Phase: I = (kVA × 1000) / (√3 × V) • Real Power: P (kW) = S (kVA) × PF • Reactive Power: Q (kVAR) = S × √(1 - PF²) • Breaker Size: ≥ 125% of full-load current Where I = current (A), V = voltage (V), S = apparent power (kVA), PF = power factor
Result: 90.21 A full-load current, 120 A breaker, 1/0 AWG wire
For 75 kVA at 480V three-phase: I = 75000 / (1.732 × 480) = 90.21 A. At PF = 0.85, real power = 63.75 kW and reactive power = 39.53 kVAR. NEC requires 125% for continuous loads, so minimum breaker is 113 A → 120 A standard size.
Apparent power, measured in kVA, represents the total electrical power flowing through a circuit — both the real power that does useful work (kW) and the reactive power that sustains electromagnetic fields in motors and transformers (kVAR). These three quantities form the power triangle: S² = P² + Q², where S is apparent power, P is real power, and Q is reactive power.
Electrical equipment like transformers, generators, and UPS systems are rated in kVA because their windings and conductors must carry the full apparent current regardless of power factor. A 100 kVA transformer at 0.8 power factor delivers only 80 kW of useful power, but the conductors must still handle the full 100 kVA current.
Single-phase power uses two conductors (line and neutral) and delivers power as P = V × I × PF. Three-phase power uses three conductors with voltages 120° apart, delivering power as P = √3 × V × I × PF. This phase relationship means three-phase delivers 73% more power than single-phase using the same wire sizes and voltage.
In commercial and industrial settings, three-phase is standard for loads above 5 kW because it is more efficient, requires smaller conductors per unit of power, and produces smoother power delivery for motors. Residential services are typically single-phase (split-phase 240/120V).
After calculating amperage, several NEC requirements affect your final design. Continuous loads (3+ hours) require 125% derating. Ambient temperature above 30°C requires ampacity correction factors. Conduit fill above three current-carrying conductors requires additional derating. Voltage drop should be limited to 3% for branch circuits and 5% for total (feeder plus branch).
kVA (kilovolt-amperes) is apparent power — the total power flowing in the circuit. kW (kilowatts) is real power — the portion that does useful work. They are related by the power factor: kW = kVA × PF. For resistive loads (PF = 1), they are equal.
Motor loads typically have PF of 0.80-0.85. Mixed commercial loads average 0.85-0.90. Resistance heaters and incandescent lighting have PF of 1.0. LED lighting is typically 0.90-0.95. If unknown, 0.85 is a common conservative estimate.
In a three-phase system, power is delivered through three conductors with 120° phase separation. The √3 factor (1.732) accounts for this phase relationship. Three-phase delivers more power per amp of line current than single-phase at the same voltage.
Per NEC Article 210.20, continuous loads (running 3+ hours) must not exceed 80% of the breaker rating. This means the breaker must be sized at 125% of the full-load current, then rounded up to the next standard size (e.g., 15, 20, 30, 40, 50, 60, 70, 80, 100, 125, 150, 200 A).
Yes — kVA to amps conversion only requires voltage and phase configuration. Power factor determines the split between real and reactive power but does not change the total current. However, PF is important for sizing generators, wiring, and understanding actual energy consumption.
Per NEC Table 310.16 (75°C copper): 14 AWG for 15A, 12 AWG for 20A, 10 AWG for 30A, 8 AWG for 40-50A, 6 AWG for 55-65A, 4 AWG for 70-85A, 2 AWG for 95-115A, 1/0 AWG for 125-150A. Always consult local codes.