How do I convert amps to watts?

Multiply amps by volts: Watts = Amps x Volts. For AC circuits also multiply by the power factor: Watts = Amps x Volts x Power Factor. For three-phase line-to-line: Watts = 1.732 x Amps x Volts x Power Factor.

What is the NEC 80% rule for breaker sizing?

NEC 210.20 requires that breakers serving continuous loads must not be loaded above 80% of rated ampacity. A 20A breaker can carry only 16A of continuous load. This calculator divides your entered amps by 0.80 and rounds up to the next standard breaker size.

What is apparent power and how is it different from real power?

Real power (watts) is the power that does useful work. Apparent power (volt-amperes, VA) is simply amps times volts, before power factor is applied. For DC and purely resistive AC loads they are equal. For inductive AC loads, apparent power is higher than real power, and the gap is reactive power.

What is a power triangle?

A power triangle is a right triangle showing the relationship between real power (P), reactive power (Q), and apparent power (S) in an AC circuit. P forms the base, Q forms the height, and S forms the hypotenuse, related by S squared equals P squared plus Q squared.

What is power factor and why does it matter?

Power factor (PF) is the ratio of real power (watts) to apparent power (volt-amps). A PF of 1.0 means all current is doing useful work. Motors and inductive loads draw more apparent power than their real wattage alone indicates because PF is less than 1.0.

What is the difference between single-phase and three-phase power?

Single-phase uses one hot conductor and is standard for residential and light commercial circuits at 120V or 240V. Three-phase uses three hot conductors and is used for motors, commercial HVAC, and EV chargers at 208V, 277V, or 480V.

What is the difference between line-to-line and line-to-neutral voltage?

Line-to-line voltage is measured between any two of the three hot conductors in a three-phase system. Line-to-neutral voltage is measured between one hot conductor and neutral. The amps to watts formula differs: line-to-line uses 1.732 as a multiplier, line-to-neutral uses 3.

How do I find the minimum wire gauge for my circuit?

This calculator references NEC 310 copper ampacity at 75 degrees C directly against your entered amps. Standard values: 14 AWG to 15A, 12 AWG to 20A, 10 AWG to 30A, 8 AWG to 50A, 6 AWG to 65A, 4 AWG to 85A. Always verify with a licensed electrician.

Amps to Watts Calculator — DC, AC Single & Three-Phase

⚠ Common Mistakes

Entering an AC peak (not RMS) value into Current or Voltage.
Leaving power factor at 1.0 for a motor or other inductive load, which overstates real power and understates current draw.
Using line-to-line voltage in the three-phase line-to-neutral formula (or vice versa).
Using a device's nameplate/rated wattage instead of its actual running wattage when reverse-checking amps.

Enter current and voltage. Formula: P = I × V

Current (I)

Voltage (V) — preset or custom

🔄 Watts to AmpsReverse of this tool

Real Power

—

Watts (W)

Kilowatts

—

Apparent Power

—

Volt-Amps (VA)

Reactive Power

—

VAR

Current

—

Amps (A)

Voltage

—

Volts (V)

Formula: —

⚡ Min. Breaker Size

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NEC 80% continuous load rule (NEC 210.20) · sized from entered amps

🔌 Min. Wire Gauge

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NEC 310 copper ampacity at 75°C · sized from entered amps

NEC breaker and wire gauge values are minimum recommendations for reference purposes only. All sizing must be independently verified by a licensed electrician in accordance with the National Electrical Code and applicable local Authority Having Jurisdiction requirements before any electrical work is performed.

Power Rectangle

Width is Current, height is Voltage. The shaded area is Power: P = I × V.

Results are for reference and estimation only. Verify all values before use in any electrical installation. See full disclaimer below.

Voltage	System Type	Common Applications
120V	Single-phase AC	Standard receptacles, small appliances, lighting branch circuits
208V	Single-phase from 3-phase panel	Small HVAC, commercial kitchen equipment, some lighting panels
240V	Single-phase AC	Large HVAC, electric water heaters, commercial dryers, EV Level 2 chargers
277V	Single-phase from 480V 3-phase system	Commercial and industrial LED/fluorescent lighting — warehouses, offices, retail
480V	Three-phase AC	Large motors, industrial HVAC, EV fast chargers, manufacturing equipment

Typical amp draws for common commercial and industrial equipment. Values are estimates — always verify against the actual equipment nameplate or specification sheet. Search by equipment name, category, or voltage.

Equipment	Category	Typical Load	Typical Voltage	Est. Amps
LED Recessed Downlight, 6-in	Lighting	10–15 W	120V	0.08–0.13 A
LED Recessed Downlight, 8-in	Lighting	15–25 W	120V	0.13–0.21 A
LED Troffer 2×2, 25W	Lighting	25 W	120–277V	0.09–0.21 A
LED Troffer 2×4, 40W	Lighting	40 W	120–277V	0.14–0.33 A
LED High Bay, 150W	Lighting	150 W	277V	~0.54 A
LED High Bay, 300W	Lighting	300 W	277V	~1.08 A
LED Shoebox / Parking Lot, 150W	Lighting	150 W	120–277V	0.54–1.25 A
LED Wall Pack, 40W	Lighting	40 W	120–277V	0.14–0.33 A
Rooftop HVAC Unit, 5-ton	HVAC	~6,000 W	208/240V	25–29 A
Rooftop HVAC Unit, 10-ton	HVAC	~11,000 W	480V 3-phase	~14.8 A
Rooftop HVAC Unit, 20-ton	HVAC	~22,000 W	480V 3-phase	~29.5 A
Mini-Split AC, 12,000 BTU	HVAC	~1,200 W	208/240V	5–6 A
Electric Unit Heater, 5 kW	HVAC	5,000 W	208/240V	20.8–24 A
Level 2 EV Charger, 7.2 kW	EV Charging	7,200 W	208/240V	30–35 A
Level 2 EV Charger, 11.5 kW	EV Charging	11,500 W	208/240V	48–55 A
DC Fast Charger, 50 kW	EV Charging	50,000 W	480V 3-phase	~67 A
DC Fast Charger, 150 kW	EV Charging	150,000 W	480V 3-phase	~200 A
3-Phase Motor, 1 HP	Motor	~746 W	480V 3-phase	~1.0 A
3-Phase Motor, 5 HP	Motor	~3,730 W	480V 3-phase	~5.0 A
3-Phase Motor, 10 HP	Motor	~7,460 W	480V 3-phase	~10 A
3-Phase Motor, 25 HP	Motor	~18,650 W	480V 3-phase	~24.9 A
3-Phase Motor, 50 HP	Motor	~37,300 W	480V 3-phase	~49.8 A
Commercial Refrigerator	Kitchen	200–500 W	120V	1.7–4.2 A
Commercial Dishwasher	Kitchen	2,000–5,000 W	240V	8.3–20.8 A
Commercial Electric Range	Kitchen	8,000–12,000 W	240V	33–50 A
Commercial Convection Oven	Kitchen	5,000–9,000 W	208/240V	20.8–43 A
Commercial Microwave, Heavy-Duty	Kitchen	1,800–3,000 W	120/208V	8.7–25 A
Desktop Computer + Monitor	Office	150–400 W	120V	1.25–3.3 A
Office Laser Printer	Office	400–1,200 W	120V	3.3–10 A
Server Rack, 1U (typical)	Office	200–500 W	120/208V	1–4.2 A
UPS, 1 kVA	Office	~700 W	120V	~5.8 A
Electric Water Heater, 40-gal	Water	4,500 W	240V	18.75 A
Commercial Electric Water Heater, 80-gal	Water	6,000–9,000 W	240V	25–37.5 A
Tankless Electric Water Heater	Water	10,000–27,000 W	240V	41.7–112.5 A

No equipment matched your search. Try a different keyword.

Estimated amp values at PF = 1.0 for resistive loads; PF = 0.85–0.90 for motors and mixed commercial loads. Always use nameplate data for final design. Values based on NEC 430 motor amp tables and NEC 310 ampacity guidance.

Amps to Watts Calculator

How to Use the Amps to Watts Calculator

Frequently Asked Questions

Amps to Watts Calculator

How to Use the Amps to Watts Calculator

Frequently Asked Questions

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