Watts to Amps Calculator

Convert watts to amps instantly for DC, AC single-phase, and AC three-phase circuits. Enter your power load and voltage to get current in amps and milliamps, the exact formula used, a minimum NEC-compliant breaker size, and a minimum wire gauge per NEC 310. A searchable commercial equipment load reference table is included for job-site reference.

Enter power and voltage. Formula: I = P ÷ V

Power (P)

Voltage (V) — preset or custom

🔄 Amps to WattsReverse of this tool

Current

—

Amps (A)

Milliamps

—

Power

—

Watts (W)

Voltage

—

Volts (V)

Formula: —

⚡ Min. Breaker Size

—

NEC 80% continuous load rule (NEC 210.20)

🔌 Min. Wire Gauge

—

NEC 310 copper ampacity at 75°C

The breaker and wire gauge shown here are minimums taken from the amps this page calculated from watts. 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 Breakdown

Real Power (W) Reactive Component (approx)

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

How to Use the Watts to Amps Calculator

Select Your Current Type

Choose DC when the wattage is a battery load, a solar load, or another direct-current load. The amps are then that wattage divided by the voltage. Choose AC Single-Phase when the wattage is on a 120V or 240V branch. Choose AC Three-Phase when the wattage belongs to a motor, commercial HVAC, an EV charger, or other equipment at 208V, 277V, or 480V.

Enter Power and Voltage

Type the power load from the equipment nameplate in watts or kilowatts. 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 — current in amps and milliamps, the exact formula with substituted values, a minimum NEC-compliant breaker size based on the 80% continuous load rule, and a minimum wire gauge per NEC 310 copper ampacity at 75°C. Use the Print button to capture results for job documentation.

Look Up Equipment in the Reference Table

Expand the Commercial Equipment Load Reference Table to find typical amp draws for LED fixtures, HVAC units, EV chargers, motors, commercial kitchen equipment, and more. Use the search box to filter by equipment type, category, or voltage. Values are starting points — always verify against the actual nameplate or spec sheet for design and installation work.

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 nameplate wattage has been turned into amps. Each row gives a typical load and an estimated amp draw at a typical voltage, so the current this page calculated can be compared with that equipment. 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 this page calculated from watts. 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 watts to amps?

Divide power in watts by the voltage in volts: Amps = Watts ÷ Volts. For AC circuits, also divide by the power factor: Amps = Watts ÷ (Volts × Power Factor). For three-phase AC using line-to-line voltage: Amps = Watts ÷ (√3 × Volts × Power Factor), where √3 ≈ 1.732. Voltage is always required — you cannot convert watts to amps 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. This page first turns the watts into amps, then divides that calculated current by 0.80 and rounds up to the next standard breaker. The breaker follows the calculated amps, not the watt figure on the nameplate. 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 power factor and why does it matter?

Power factor changes the amps a given wattage draws. At 1.0, as with a heater, the amps are watts divided by volts. A motor at 0.85 draws more amps than its wattage alone suggests, because the circuit also carries current that does not do work. Read the power factor from the equipment spec sheet. Leaving it at 1.0 on a motor understates the current and the breaker.

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

On this page, single-phase is the path that divides the wattage by the voltage to get amps. That is the usual 120V receptacle circuit or the 240V appliance circuit. Three-phase also divides by 1.732, because the same wattage is carried on three hot conductors and the current on each one is lower. Use it for a motor, a large HVAC unit, or an EV fast charger at 208V, 277V, or 480V. Pick the mode that matches how the equipment is fed. The wrong mode changes the amp result and the breaker that follows it.

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 amps change with that choice. Line-to-line divides your watts by the voltage and by the square root of 3. Line-to-neutral divides by the voltage and then by 3. A 277 volt lighting load uses the line-to-neutral setting. Entering 480 volts for that same wattage understates the current.

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

The wire size on this page follows the amps just calculated from your watts, using the copper ampacity in NEC 310 at 75°C. The watt figure is not what picks the conductor. 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. If the run is long, voltage drop can push the choice to the next size up. A licensed electrician has to review the size before it is installed.

What voltage should I use for commercial lighting circuits?

If you have the fixture wattage and the circuit is 277V, this page turns those watts into the current on that leg. 277V lighting is one leg of a 480V three-phase system, common in warehouses, offices, and retail because more fixtures fit on a circuit than they would at 120V. Do not run that lighting load at 120V in the calculator, and do not use 480V unless the fixtures are actually on the three-phase line. The amp result, and the breaker after it, follows the voltage you enter.