Amps to Watts Calculator

Convert amps to watts instantly for DC, AC single-phase, and AC three-phase circuits. Enter your current and voltage to get real power in watts and kilowatts, the exact formula used, a minimum NEC-compliant breaker size, and a minimum wire gauge per NEC 310 — sized directly from your entered amps. AC results also show apparent power, reactive power, a live power-triangle visual, and common-mistake guidance. A searchable commercial equipment load reference table is included for job-site reference.

⚠ 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

—

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

🔌 Min. Wire Gauge

—

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

The breaker and wire gauge shown here are minimums taken from the amps you entered. A licensed electrician still has to check them against the National Electrical Code (NFPA 70) and the local authority having jurisdiction before any work.

Power Rectangle

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

The wattage is an estimate from the current and voltage you entered. Check it before it is used on a job. The full disclaimer is below.

How to Use the Amps to Watts Calculator

Select Your Current Type

Choose DC when the current you have is from a battery, a solar panel, or another direct-current source. The watts are then that current times the voltage. Choose AC Single-Phase when the current is on a 120V or 240V branch. Choose AC Three-Phase when the current is on a motor, commercial HVAC, an EV charger, or other equipment at 208V, 277V, or 480V.

Enter Current and Voltage

Type the measured or rated current from a clamp meter, breaker panel, or equipment nameplate. Select a common voltage preset or enter a custom voltage. For AC circuits, set the power factor using the load-type preset — Resistive 1.0, LED drivers 0.95, typical commercial 0.90, motors full load 0.85 — or enter a custom value from the equipment spec sheet.

Review Results and NEC Recommendations

Click Calculate. Results appear immediately — real power in watts and kilowatts, the exact formula with substituted values, a minimum NEC-compliant breaker size, and a minimum wire gauge per NEC 310 — both sized directly from the amps you entered. AC circuits also show apparent power, reactive power, and a live power-triangle diagram.

Check Common Mistakes and the Equipment Table

Review the Common Mistakes box for the most frequent input errors for your selected circuit type. Expand the Commercial Equipment Load Reference Table to cross-check typical amp draws for LED fixtures, HVAC units, EV chargers, motors, and more. Use the Print button to capture results, including the power diagram, for job documentation.

Common Commercial Voltage Reference

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

Commercial Equipment Load Reference Table NEC Reference

Use this table after a measured current has been turned into watts. Each row is a typical commercial load and an estimated amp draw at a typical voltage. If the amps you entered are far from the row for that equipment, check the voltage and the power factor before you trust the wattage. The numbers are estimates. The nameplate still governs. 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.

These estimated amps are the comparison for the current you typed in. They use PF = 1.0 for resistive loads and 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.

Frequently Asked Questions

How do I convert amps to watts?

Multiply current in amps by voltage in volts: Watts = Amps × Volts. For AC circuits, also multiply by the power factor: Watts = Amps × Volts × Power Factor. For three-phase AC using line-to-line voltage: Watts = √3 × Amps × Volts × Power Factor, where √3 ≈ 1.732. Voltage is always required — you cannot convert amps to watts without it.

What is the NEC 80% rule for breaker sizing?

NEC 210.20 and NEC 215.3 say a breaker serving a continuous load may carry only 80 percent of its rating. You already have the current, so this page divides those entered amps by 0.80 and rounds up to the next standard breaker. Sixteen continuous amps call for a 20 amp breaker. Lighting, HVAC, and production loads are usually treated as continuous. A licensed electrician still has to confirm that breaker before any permitted work.

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

Real power (watts) is the power that performs useful work. Apparent power (volt-amperes, VA) is simply current multiplied by voltage, before power factor is applied. For DC circuits and purely resistive AC loads, the two are equal. For AC loads with a power factor below 1.0 — motors, ballasts, and other inductive equipment — apparent power is always higher than real power, and equipment such as transformers, generators, and service panels must be sized to the higher apparent-power figure, not just the real-power figure.

What is a power triangle?

A power triangle is a right triangle that shows how real power (P), reactive power (Q), and apparent power (S) relate in an AC circuit. Real power forms the base, reactive power forms the height, and apparent power forms the hypotenuse, following the Pythagorean relationship S² = P² + Q². The angle between the base and the hypotenuse is the phase angle, and its cosine is the power factor. This calculator draws the triangle live from your AC results.

What is power factor and why does it matter?

Power factor changes the watts you get from a given current. At 1.0, as with a heater, the watts equal amps times volts. A motor at 0.85 produces fewer watts from the same current, because part of that current is not doing work. Read the power factor from the equipment spec sheet. Leaving it at 1.0 on a motor overstates the wattage.

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

On this page, single-phase is the path that multiplies the amps you entered by the voltage to get watts. That is the usual 120V receptacle circuit or the 240V appliance circuit. Three-phase also multiplies by 1.732, because that current is shared across three hot conductors on a motor, a large HVAC unit, or an EV fast charger at 208V, 277V, or 480V. A building often has both supplies. Pick the mode that matches the current you measured, not the mode that produces the larger watt number.

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

Line-to-line voltage is measured between two hot conductors, such as 480 volts. Line-to-neutral is measured from one hot conductor to neutral, which is 277 volts on that same system. On this page the watts change with that choice. Line-to-line multiplies your amps by the voltage and by the square root of 3. Line-to-neutral multiplies by the voltage and then by 3. Commercial lighting is usually the 277 volt line-to-neutral case. Set the three-phase control to the voltage you actually measured, or the wattage will be wrong.

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

The wire size on this page is read from the amps you typed, using the copper ampacity in NEC 310 at 75°C. There is no wattage step in between. At that temperature the usual matches are 14 AWG for 15 amps, 12 AWG for 20 amps, 10 AWG for 30 amps, 8 AWG for 50 amps, 6 AWG for 65 amps, 4 AWG for 85 amps, 2 AWG for 115 amps, 1/0 AWG for 150 amps, 2/0 AWG for 175 amps, and 3/0 AWG for 200 amps. A long run can need a larger size because of voltage drop. A licensed electrician has to review the size before it is installed.

What voltage should I use for commercial lighting circuits?

If the lighting circuit is 277V, enter that voltage with the current you measured on one leg. This page turns that current into watts for the fixtures on the circuit. 277V is one leg of a 480V three-phase system, which is why warehouses and retail often use it for LED and fluorescent lighting. Receptacles on the same job are usually 120V, and a large HVAC unit or fast charger is usually 480V three-phase. The wattage matches the job only when the voltage matches the circuit you metered.