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Convert apparent power in volt-amps (VA) to electrical current in amperes (A) for single-phase and three-phase AC circuits.
Line voltage
Where A is current in amperes, VA is apparent power in volt-amps, and V is voltage in volts.
√3 ≈ 1.732. V is the line-to-line voltage in three-phase systems.
| Power (VA) | 120V | 208V | 240V | 277V |
|---|---|---|---|---|
| 100 VA | 0.83 A | 0.48 A | 0.42 A | 0.36 A |
| 500 VA | 4.17 A | 2.40 A | 2.08 A | 1.81 A |
| 1,000 VA | 8.33 A | 4.81 A | 4.17 A | 3.61 A |
| 1,500 VA | 12.50 A | 7.21 A | 6.25 A | 5.42 A |
| 2,000 VA | 16.67 A | 9.62 A | 8.33 A | 7.22 A |
| 3,000 VA | 25.00 A | 14.42 A | 12.50 A | 10.83 A |
| 5,000 VA | 41.67 A | 24.04 A | 20.83 A | 18.05 A |
| 10,000 VA | 83.33 A | 48.08 A | 41.67 A | 36.10 A |
| Power (VA) | 208V | 240V | 480V |
|---|---|---|---|
| 1,000 VA | 2.78 A | 2.41 A | 1.20 A |
| 3,000 VA | 8.33 A | 7.22 A | 3.61 A |
| 5,000 VA | 13.88 A | 12.03 A | 6.01 A |
| 10,000 VA | 27.76 A | 24.06 A | 12.03 A |
| 15,000 VA | 41.64 A | 36.08 A | 18.04 A |
| 25,000 VA | 69.39 A | 60.14 A | 30.07 A |
| 50,000 VA | 138.79 A | 120.28 A | 60.14 A |
| 100,000 VA | 277.58 A | 240.56 A | 120.28 A |
| 150,000 VA | 416.37 A | 360.84 A | 180.42 A |
VA to amps conversion is the process of determining the electrical current (measured in amperes) that a device or circuit draws, given its apparent power rating in volt-amperes (VA). Apparent power represents the total power flowing in an AC circuit, combining both the real power that performs useful work and the reactive power that sustains magnetic and electric fields. This conversion is essential for electricians, engineers, and facility managers who need to determine whether circuits, wiring, and protective devices can safely handle the current demanded by equipment such as UPS systems, transformers, and motor loads. By dividing VA by voltage for single-phase systems, or by voltage multiplied by the square root of three for three-phase systems, you can accurately size circuit breakers, conductors, and other protective components.
Find the apparent power rating on the equipment nameplate, product documentation, or specifications sheet. This value is typically listed in VA or kVA (multiply kVA by 1,000 to get VA).
Identify the operating voltage of your circuit. Common voltages include 120V and 240V for single-phase residential, 208V for commercial single-phase, and 208V, 240V, or 480V for three-phase industrial systems.
For single-phase circuits, use A = VA ÷ V. For three-phase circuits, use A = VA ÷ (√3 × V), where √3 equals approximately 1.732. The three-phase formula accounts for power being distributed across three conductors.
For continuous loads (operating 3+ hours), multiply the calculated amps by 1.25 per NEC Article 210.20. This ensures your breaker and wiring are rated for sustained operation without overheating.
Knowing the current draw allows you to select the correct breaker size, preventing nuisance tripping from undersized breakers or fire hazards from oversized ones.
Accurate amperage calculations ensure conductors are large enough to carry the load safely, preventing voltage drop over long runs and reducing the risk of insulation damage from overheating.
Data centers and industrial facilities must aggregate current draws across all equipment to ensure panels, feeders, and utility services are adequately sized for the total demand.
| Equipment | Typical VA | Amps @ 120V | Amps @ 240V |
|---|---|---|---|
| Desktop Computer | 300-500 VA | 2.5-4.2 A | 1.25-2.1 A |
| Server (1U Rack) | 500-1000 VA | 4.2-8.3 A | 2.1-4.2 A |
| Network Switch (48-port) | 150-400 VA | 1.25-3.3 A | 0.63-1.7 A |
| UPS (Small Office) | 1500 VA | 12.5 A | 6.25 A |
| Industrial Motor (5 HP) | 5000 VA | 41.7 A | 20.8 A |
| LED Monitor (27") | 40-80 VA | 0.33-0.67 A | 0.17-0.33 A |
| Laser Printer | 600-1200 VA | 5.0-10.0 A | 2.5-5.0 A |
| Transformer (75 kVA) | 75,000 VA | 625 A | 312.5 A |
| HVAC Unit (3 ton) | 4500-6000 VA | 37.5-50.0 A | 18.75-25.0 A |
| Welding Machine | 8000-12000 VA | 66.7-100.0 A | 33.3-50.0 A |
VA measures apparent power, which includes both the useful real power (watts) and the reactive power that flows back and forth in AC circuits. When calculating amps from VA, you get the total current the circuit must carry. When calculating amps from watts, you only account for the current doing useful work. For equipment sizing and circuit protection, using VA gives you the more conservative and safer amperage figure.
Convert the new equipment's VA rating to amps using the appropriate formula for your system type. Then compare the total amps (existing load plus new equipment) against the panel's main breaker rating. Residential panels are typically 100A or 200A at 240V. The total connected load should not exceed 80% of the panel rating for continuous loads per NEC guidelines.
Since VA equals volts multiplied by amps, increasing voltage proportionally decreases the current for the same power. This is why high-voltage distribution (e.g., 480V industrial) is preferred for large loads: it reduces current, allowing smaller and less expensive conductors while minimizing power losses in the wiring.
In DC circuits, there is no reactive component, so VA and watts are identical. The simple formula A = W ÷ V applies directly. The VA designation is primarily meaningful for AC circuits where current and voltage waveforms may be out of phase, creating a difference between apparent and real power.
Inrush current, the brief surge when motors and transformers energize, can be 6 to 10 times the steady-state current. While VA ratings reflect steady-state operation, you should consider inrush when selecting breaker types. Use slow-blow fuses or Type D breakers for motor loads, and ensure your UPS or generator can handle momentary surges above their nominal VA rating.