Amps to Watts Calculator
Convert amps to watts at any voltage and see how much power a circuit actually delivers for DC, AC single-phase, and three-phase loads. Use it to compare appliance capacity, plan generator loads, or verify that a breaker can handle what you want to run.
What Is Amps to Watts?
Amps measure how much current flows through a circuit. Watts measure how much power that current delivers. Converting amps to watts answers the question: "How much power does this circuit provide?" This is critical for understanding energy consumption, comparing appliances, and verifying that your electrical system can handle the load.
The Formulas
DC (Direct Current)
Used for battery circuits, solar panels, and automotive systems. No power factor involved because DC voltage and current stay in phase.
AC Single Phase
Used for standard residential circuits (120V and 240V). Real power is always less than or equal to apparent power (V × I) because reactive loads consume current without doing work. Typical PF values: 1.0 for heaters, 0.85 for mixed loads, 0.65-0.80 for motors.
AC Three Phase
Used for commercial and industrial equipment at 208V, 400V, or 480V line-to-line. The √3 factor (1.732) comes from the line-to-line vs line-to-neutral relationship in a balanced three-phase system. Amps in this formula is the line current (what a clamp meter on one conductor reads), and the result is the total real power delivered across the three line conductors, not a per-line figure. For a 20A line current at 480V L-L on PF 0.85 that works out to about 14,133W total, or 1.732 × 480 × 20 × 0.85. At 208V L-L on PF 0.85 the same 20A line current delivers about 6,125W total across the three conductors. The voltage you plug into the formula is always the line-to-line value; if you only know the line-to-neutral value, multiply by √3 first.
Note: 277V is not a three-phase L-L voltage on this site. It's the line-to-neutral leg of a 480Y/277V wye system and is almost always used as a single-phase lighting branch, so 277V queries route through the single-phase formula above.
Circuit Capacity by Breaker Size
These wattage figures are the real power a resistive AC load at PF 1.0 would see on each breaker rating at 120V and 240V. NEC 210.19(A) sizes the conductor and OCP at 125% of any continuous load (equivalently 80% of the breaker rating), so the "Continuous (80%)" column names the sizing threshold the code points at for continuous loads, not a code-required maximum for all loads. Non-continuous loads can use the full rating. Actual install pick depends on whether the load is continuous, the equipment nameplate, and the conductor temperature rating.
| Breaker | At 120V | Continuous (80%) | At 240V | Continuous (80%) |
|---|---|---|---|---|
| 15A | 1,800W | 1,440W | 3,600W | 2,880W |
| 20A | 2,400W | 1,920W | 4,800W | 3,840W |
| 30A | 3,600W | 2,880W | 7,200W | 5,760W |
| 40A | 4,800W | 3,840W | 9,600W | 7,680W |
| 50A | 6,000W | 4,800W | 12,000W | 9,600W |
Quick Results Table
Each column uses the primary interpretation for its voltage so the table lines up with the result pages: 12V as DC, 120/230/240V as AC single-phase at PF 1.0 resistive, 208/480V as AC three-phase L-L at PF 0.85. Three-phase cells show the total real power delivered across the three line conductors (not a per-line figure) for a given line current in the Amps column. Click any cell for the full breakdown.
| Amps | 12V DC | 120V 1Φ PF 1.0 | 208V 3Φ L-L PF 0.85 | 230V 1Φ PF 1.0 | 240V 1Φ PF 1.0 | 480V 3Φ L-L PF 0.85 |
|---|---|---|---|---|---|---|
| 1A | 12W | 120W | 306.23W | 230W | 240W | 706.68W |
| 2A | 24W | 240W | 612.45W | 460W | 480W | 1,413.35W |
| 5A | 60W | 600W | 1,531.13W | 1,150W | 1,200W | 3,533.38W |
| 10A | 120W | 1,200W | 3,062.27W | 2,300W | 2,400W | 7,066.77W |
| 15A | 180W | 1,800W | 4,593.4W | 3,450W | 3,600W | 10,600.15W |
| 20A | 240W | 2,400W | 6,124.53W | 4,600W | 4,800W | 14,133.53W |
| 30A | 360W | 3,600W | 9,186.8W | 6,900W | 7,200W | 21,200.3W |
| 40A | 480W | 4,800W | 12,249.06W | 9,200W | 9,600W | 28,267.07W |
| 50A | 600W | 6,000W | 15,311.33W | 11,500W | 12,000W | 35,333.84W |
| 100A | 1,200W | 12,000W | 30,622.66W | 23,000W | 24,000W | 70,667.67W |
Related Calculators
Frequently Asked Questions
Standards & References
This page cites the following electrical codes and standards. Always consult the current edition of your local adopted standard for authoritative requirements.
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NEC Table 310.16.
Allowable ampacities of insulated conductors rated up to 2000V, 60°C through 90°C, not more than three current-carrying conductors in raceway or cable.
National Electrical Code (NFPA 70), Article 310, Conductors for General Wiring. Reference → -
NEC 240.4(D).
Small conductor rule: overcurrent protection shall not exceed 15A for 14 AWG, 20A for 12 AWG, and 30A for 10 AWG copper, regardless of ampacity table values.
National Electrical Code (NFPA 70), Article 240, Overcurrent Protection. Reference → -
IEC 60038.
IEC standard voltages. Defines 230/400V as the nominal low-voltage supply for 50Hz systems, which harmonized European residential supply in 1995.
International Electrotechnical Commission. Reference →
Disclaimer: The information on this page is provided for reference. Always consult a licensed electrician and the current edition of your local adopted electrical code before performing electrical work.