kVA to Amps Calculator

About the kVA to Amps Calculator

A kVA to amps calculator converts apparent power in kilovolt-amperes to current in amperes for single-phase and three-phase AC systems. This conversion is essential when you have a generator, transformer, or UPS specification in kVA and need to know the ampere rating for connecting cables, circuit breakers, and switchgear. Generator and transformer manufacturers universally rate their equipment in kVA, leaving the current calculation to the installer. Getting this wrong can result in undersized wiring that overheats or circuit breakers that trip under legitimate load. Our free kVA to amps calculator supports every standard voltage configuration: 120V, 208V, 240V, 277V, and 480V for US installations; 230V and 400V for European and UK systems; 415V for Australian and New Zealand three-phase. It calculates amps for both single-phase and three-phase, with a side-by-side comparison of both configurations. This tool is used daily by electrical contractors, equipment installers, and facilities engineers worldwide.

How It Works

Single-phase: A = (kVA × 1000) / V. Three-phase: A = (kVA × 1000) / (V × √3). The kVA-to-amps calculation does not require power factor because kVA already represents apparent power (voltage × current, without PF). Example 1 (single-phase): 10 kVA at 240V: A = (10 × 1000) / 240 = 41.67A. Example 2 (3-phase commercial): 25 kVA at 208V: A = (25 × 1000) / (208 × 1.732) = 25,000 / 360.25 = 69.4A. Example 3 (3-phase, AU): 50 kVA at 415V: A = (50 × 1000) / (415 × 1.732) = 50,000 / 718.78 = 69.6A. For sizing circuit breakers and conductors, multiply the calculated amps by 125% for continuous loads (NEC 215.3): 41.67A × 1.25 = 52.1A → 60A breaker. Cable sizing uses the calculated amps against the conductor ampacity tables in NEC 310.15 or IEC 60364-5-52.

Tips & Best Practices

• ✓Standard generator connection sizes: 5 kVA at 240V = 20.8A (30A outlet standard); 7.5 kVA = 31.3A (50A outlet common); 10 kVA = 41.7A (60A circuit). Most portable generators ship with 30A and 50A outlets; verify before connecting.
• ✓Three-phase transformer secondary connections: the calculated amps is per-phase current. For balanced 3-phase loads, all three phases carry the same current. For single-phase loads connected to a 3-phase panel, only one or two phases are loaded — always aim for balanced phase loading.
• ✓Transformer inrush current: when a transformer first energizes, the inrush current can reach 10-12× rated current for 0.1–0.3 seconds. Circuit breakers protecting transformers use inverse-time-delay types (typically 250% of calculated FLC) to ride through this inrush without nuisance tripping.
• ✓UK and Australia: the 415V three-phase system is 240V line-to-neutral. A 10 kVA at 415V 3-phase: A = 10,000 / (415 × 1.732) = 13.9A per phase — markedly lower than the equivalent US 208V 3-phase calculation (27.7A) for the same kVA, due to higher voltage.

Who Uses This Calculator

Electrical contractors specifying cable and breaker sizes for generator connections. Equipment installers connecting transformers, UPS systems, and large motors to existing switchgear. Facilities engineers auditing electrical panel capacity when adding new equipment. Anyone converting a generator or transformer kVA specification into the ampere values needed for connection planning.