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Amps to VA Calculator

Convert electrical current in amperes (A) to apparent power in volt-amps (VA) for single-phase and three-phase AC circuits.

Calculate VA from Amps

Circuit Type

Current (Amps)

Voltage (V)

Line voltage

Amps to VA Formulas

Single-Phase AC

VA = A × V

Where VA is apparent power in volt-amps, A is current in amperes, and V is voltage in volts.

Three-Phase AC

VA = √3 × A × V

√3 ≈ 1.732. V is the line-to-line voltage in three-phase systems.

What Is Amps to VA Conversion?

Volt-amperes (VA) measure apparent power in AC circuits — the product of voltage and current without considering power factor. Converting amps to VA is straightforward: VA = Amps × Volts for single-phase, and VA = Amps × Volts × √3 for three-phase. VA ratings are used for transformers, UPS systems, and power distribution equipment because these components must handle the full current regardless of power factor. Understanding VA helps in sizing electrical infrastructure, selecting backup power systems, and evaluating the total demand on power sources.

How to Calculate Amps to VA Conversion

1
Identify System Phase
Determine if your system is single-phase or three-phase. Single-phase has two wires (line and neutral) or two lines. Three-phase has three line conductors.
2
Measure or Find Amperage
Use a clamp meter to measure current or find the rated amps on equipment nameplates. For multiple loads, sum individual currents on the same phase.
3
Enter System Voltage
Input the supply voltage. For single-phase: 120V or 240V. For three-phase: 208V, 240V, 480V, or 600V line-to-line.
4
Read VA Result
The calculator outputs apparent power in VA. Divide by 1000 for kVA. This value is used directly for sizing transformers, UPS systems, and power distribution equipment.

Why Amps to VA Conversion Matters

UPS Sizing

UPS systems are primarily rated in VA. Converting your total load amps to VA ensures the UPS can supply adequate apparent power to all connected equipment, including reactive power for inductive loads.

Transformer Loading

Transformer capacity is specified in VA or kVA. Exceeding the VA rating causes overheating regardless of the real power (kW) drawn. Proper amps-to-VA conversion prevents transformer overloading.

Power Strip and PDU Ratings

Power distribution units (PDUs) in data centers are rated in VA. Converting server and network equipment amps to VA ensures PDU circuits are not overloaded.

Electrical Code Compliance

NEC load calculations for branch circuits and feeders often use VA as the unit of measure. Converting equipment amps to VA is required for code-compliant panel schedule calculations.

Electrical Safety Tips & Best Practices

VA Is Always ≥ Watts

Since VA = Watts ÷ Power Factor, and power factor is ≤ 1, the VA rating always equals or exceeds the watt rating. Size equipment based on VA, not watts, to handle the full current demand.

UPS Runtime Uses Watts

While UPS capacity is rated in VA, battery runtime depends on real power (watts). A 1000VA UPS with 0.9 PF can deliver 900W. Check both VA capacity and watt rating when sizing UPS systems.

Phase Current vs Line Current

In three-phase delta configurations, phase current differs from line current. Always use line current (measured on the main conductors) for amps-to-VA calculations.

Derating for Harmonics

Non-linear loads (computers, VFDs, LED drivers) generate harmonic currents that increase VA demand beyond fundamental frequency calculations. Derate transformers to 80% for heavy harmonic loads.

Single-Phase Amps to VA Conversion Chart

Current (A)	120V	208V	240V	277V
1 A	120 VA	208 VA	240 VA	277 VA
5 A	600 VA	1,040 VA	1,200 VA	1,385 VA
10 A	1,200 VA	2,080 VA	2,400 VA	2,770 VA
15 A	1,800 VA	3,120 VA	3,600 VA	4,155 VA
20 A	2,400 VA	4,160 VA	4,800 VA	5,540 VA
30 A	3,600 VA	6,240 VA	7,200 VA	8,310 VA
50 A	6,000 VA	10,400 VA	12,000 VA	13,850 VA
100 A	12,000 VA	20,800 VA	24,000 VA	27,700 VA
200 A	24,000 VA	41,600 VA	48,000 VA	55,400 VA

Three-Phase Amps to VA Conversion Chart

Current (A)	208V	240V	480V
1 A	360 VA	416 VA	831 VA
5 A	1,801 VA	2,078 VA	4,157 VA
10 A	3,602 VA	4,157 VA	8,314 VA
15 A	5,403 VA	6,235 VA	12,471 VA
20 A	7,204 VA	8,314 VA	16,628 VA
30 A	10,806 VA	12,471 VA	24,941 VA
50 A	18,010 VA	20,785 VA	41,569 VA
100 A	36,020 VA	41,569 VA	83,138 VA
200 A	72,040 VA	83,138 VA	166,277 VA
400 A	144,079 VA	166,277 VA	332,554 VA

Frequently Asked Questions

What is the difference between VA and watts?

VA measures apparent power (voltage × current), while watts measure real power (the actual energy consumed). The ratio of watts to VA is the power factor. For resistive loads, they are equal. For inductive or capacitive loads, VA is higher than watts.

Why do UPS systems use VA ratings?

UPS systems use VA ratings because they must handle the full current flow regardless of power factor. A UPS rated at 1000 VA can deliver 1000 VA of apparent power, but the actual watts available depends on the connected load's power factor.

How do I convert VA to watts?

Multiply VA by the power factor: Watts = VA × PF. For typical computer equipment with a power factor of 0.6-0.7, a 1000 VA UPS provides about 600-700 watts of real power.

What is a typical power factor for different loads?

Resistive loads (heaters, incandescent bulbs): 1.0. Computer equipment: 0.6-0.7 without PFC, 0.95+ with active PFC. Motors: 0.7-0.9 depending on load. Fluorescent lights: 0.5-0.9.

How do I convert amps to VA?

For single-phase: VA = Amps × Volts. For three-phase: VA = Amps × Volts × 1.732. For example, 10 amps at 120V single-phase = 1200 VA. The same 10 amps at 208V three-phase = 3603 VA.

Is VA the same as watts?

No. VA (volt-amperes) measures apparent power, while watts measure real power. They are related by power factor: Watts = VA × PF. For resistive loads (heaters), VA ≈ Watts. For reactive loads (motors), VA > Watts because current and voltage are not perfectly in phase.

What size UPS do I need for 5 amps at 120V?

At 120V, 5 amps = 600 VA. Select a UPS rated at least 750 VA (next standard size up) to provide headroom. Standard UPS sizes are 500, 750, 1000, 1500, 2000, and 3000 VA. Always size 20-30% above calculated VA.

Why are transformers rated in VA instead of watts?

Transformers must handle the total current (apparent power) flowing through their windings, regardless of power factor. The winding copper and core iron losses depend on current magnitude, not whether that current does useful work. VA rating ensures the transformer can handle any power factor load.

How do I convert VA to kVA?

Divide VA by 1000. For example, 5000 VA = 5 kVA. Standard transformer kVA sizes include 15, 25, 37.5, 50, 75, 100, 150, 225, 300, 500, 750, and 1000 kVA.

References & Industry Standards

NEC Article 220 - Branch-Circuit, Feeder, and Service Load Calculations
IEEE C62.45 - IEEE Recommended Practice on Surge Testing for Equipment Connected to Low-Voltage AC Power Circuits
IEC 62040 - Uninterruptible Power Systems (UPS)
NEMA PE 1 - Uninterruptible Power Systems

Last updated: 2026-02-01 | Reviewed by UnitTables Engineering Team

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What Is Amps to VA Conversion?

How to Calculate Amps to VA Conversion

Identify System Phase

Determine if your system is single-phase or three-phase. Single-phase has two wires (line and neutral) or two lines. Three-phase has three line conductors.

Measure or Find Amperage

Use a clamp meter to measure current or find the rated amps on equipment nameplates. For multiple loads, sum individual currents on the same phase.

Enter System Voltage

Input the supply voltage. For single-phase: 120V or 240V. For three-phase: 208V, 240V, 480V, or 600V line-to-line.

Read VA Result

The calculator outputs apparent power in VA. Divide by 1000 for kVA. This value is used directly for sizing transformers, UPS systems, and power distribution equipment.

Why Amps to VA Conversion Matters

UPS Sizing

Transformer Loading

Transformer capacity is specified in VA or kVA. Exceeding the VA rating causes overheating regardless of the real power (kW) drawn. Proper amps-to-VA conversion prevents transformer overloading.

Power Strip and PDU Ratings

Power distribution units (PDUs) in data centers are rated in VA. Converting server and network equipment amps to VA ensures PDU circuits are not overloaded.

Electrical Code Compliance

NEC load calculations for branch circuits and feeders often use VA as the unit of measure. Converting equipment amps to VA is required for code-compliant panel schedule calculations.

Electrical Safety Tips & Best Practices

VA Is Always ≥ Watts

Since VA = Watts ÷ Power Factor, and power factor is ≤ 1, the VA rating always equals or exceeds the watt rating. Size equipment based on VA, not watts, to handle the full current demand.

UPS Runtime Uses Watts

While UPS capacity is rated in VA, battery runtime depends on real power (watts). A 1000VA UPS with 0.9 PF can deliver 900W. Check both VA capacity and watt rating when sizing UPS systems.

Phase Current vs Line Current

In three-phase delta configurations, phase current differs from line current. Always use line current (measured on the main conductors) for amps-to-VA calculations.

Derating for Harmonics

Non-linear loads (computers, VFDs, LED drivers) generate harmonic currents that increase VA demand beyond fundamental frequency calculations. Derate transformers to 80% for heavy harmonic loads.

Single-Phase Amps to VA Conversion Chart

Current (A)	120V	208V	240V	277V
1 A	120 VA	208 VA	240 VA	277 VA
5 A	600 VA	1,040 VA	1,200 VA	1,385 VA
10 A	1,200 VA	2,080 VA	2,400 VA	2,770 VA
15 A	1,800 VA	3,120 VA	3,600 VA	4,155 VA
20 A	2,400 VA	4,160 VA	4,800 VA	5,540 VA
30 A	3,600 VA	6,240 VA	7,200 VA	8,310 VA
50 A	6,000 VA	10,400 VA	12,000 VA	13,850 VA
100 A	12,000 VA	20,800 VA	24,000 VA	27,700 VA
200 A	24,000 VA	41,600 VA	48,000 VA	55,400 VA

Three-Phase Amps to VA Conversion Chart

Current (A)	208V	240V	480V
1 A	360 VA	416 VA	831 VA
5 A	1,801 VA	2,078 VA	4,157 VA
10 A	3,602 VA	4,157 VA	8,314 VA
15 A	5,403 VA	6,235 VA	12,471 VA
20 A	7,204 VA	8,314 VA	16,628 VA
30 A	10,806 VA	12,471 VA	24,941 VA
50 A	18,010 VA	20,785 VA	41,569 VA
100 A	36,020 VA	41,569 VA	83,138 VA
200 A	72,040 VA	83,138 VA	166,277 VA
400 A	144,079 VA	166,277 VA	332,554 VA

Frequently Asked Questions

What is the difference between VA and watts?

Why do UPS systems use VA ratings?

How do I convert VA to watts?

Multiply VA by the power factor: Watts = VA × PF. For typical computer equipment with a power factor of 0.6-0.7, a 1000 VA UPS provides about 600-700 watts of real power.

What is a typical power factor for different loads?

Resistive loads (heaters, incandescent bulbs): 1.0. Computer equipment: 0.6-0.7 without PFC, 0.95+ with active PFC. Motors: 0.7-0.9 depending on load. Fluorescent lights: 0.5-0.9.

How do I convert amps to VA?

For single-phase: VA = Amps × Volts. For three-phase: VA = Amps × Volts × 1.732. For example, 10 amps at 120V single-phase = 1200 VA. The same 10 amps at 208V three-phase = 3603 VA.

Is VA the same as watts?

What size UPS do I need for 5 amps at 120V?

Why are transformers rated in VA instead of watts?

How do I convert VA to kVA?

Divide VA by 1000. For example, 5000 VA = 5 kVA. Standard transformer kVA sizes include 15, 25, 37.5, 50, 75, 100, 150, 225, 300, 500, 750, and 1000 kVA.

References & Industry Standards

NEC Article 220 - Branch-Circuit, Feeder, and Service Load Calculations

IEEE C62.45 - IEEE Recommended Practice on Surge Testing for Equipment Connected to Low-Voltage AC Power Circuits

IEC 62040 - Uninterruptible Power Systems (UPS)

NEMA PE 1 - Uninterruptible Power Systems

Last updated: 2026-02-01 | Reviewed by UnitTables Engineering Team