Amps to VA Calculator

About the Amps to VA Calculator

An amps to VA calculator converts current in amperes to apparent power in volt-amperes — the unit used to rate circuit breakers, wiring, UPS units, power strips, and outlet capacity. Volt-amperes (VA) is simply the product of RMS voltage and RMS current without power factor correction, making it the most direct measure of what a circuit must physically carry. While watts measure the useful work done and kVA is used for large equipment, VA is the standard for smaller devices: a 1,500 VA UPS, a 600 VA transformer, a 1,800 VA circuit. Understanding VA is essential for determining whether a circuit can safely support a given load, sizing wiring according to NEC or IEC standards, and selecting UPS units for computers and sensitive electronics. Our free amps to VA calculator works for single-phase and three-phase circuits, supporting standard voltages from 12V DC-equivalent calculations to 480V three-phase industrial systems used across the USA, UK, Canada, Australia, and EU.

How It Works

Single-phase: VA = A × V. Three-phase: VA = A × V × √3. Example 1: 15A circuit at 120V: VA = 15 × 120 = 1,800 VA. This is the maximum apparent power the circuit can deliver at full current. Example 2 (3-phase): 20A at 208V: VA = 20 × 208 × 1.732 = 7,205 VA (7.2 kVA). Converting to kVA: divide by 1,000. Converting to kW: multiply by power factor. NEC 80% loading rule: a 1,800 VA circuit should be loaded to no more than 1,800 × 0.8 = 1,440 VA for continuous loads. Circuit breaker sizing: the breaker ampere rating determines maximum VA = breaker amps × voltage. A 20A, 120V circuit = 2,400 VA maximum; continuous load limit = 1,920 VA.

Tips & Best Practices

• ✓The NEC 80% continuous load rule: for loads that operate for 3+ hours continuously (always-on equipment, EV charging, server rooms), limit loading to 80% of the circuit's VA capacity. A 15A, 120V circuit (1,800 VA) should carry no more than 1,440 VA continuously.
• ✓UPS VA ratings are not the same as watt ratings. A 1,500 VA UPS may be rated for 900W (PF 0.6) or 1,350W (PF 0.9) depending on the model. Check both VA and watt specifications before purchase — your server's power draw in watts may fit but its VA draw may exceed the UPS rating.
• ✓For LED lighting circuits, check the driver's input VA (not just wattage). A 60W LED fixture with a 0.7 power factor driver draws 60 / 0.7 = 85.7 VA. Filling a 15A (1,800 VA) circuit with LED fixtures: 1,440 VA / 85.7 VA = 16 fixtures max at 80% loading.
• ✓VA is always equal to or greater than watts. The difference is reactive power. For purely resistive loads (incandescent heaters, old-style filament bulbs), VA = W exactly. For all other modern loads, VA > W.

Who Uses This Calculator

Electricians calculating circuit loading in VA before installing additional equipment. Homeowners determining whether a circuit can support a new appliance. IT managers sizing UPS units for server rooms and network closets. Engineers performing load calculations per NEC Article 220 or IEC 60364. Anyone selecting extension cords, power strips, or outlet multipliers who needs to verify total VA loading.