Amp to Watt Calculator
Convert amps to watts for DC and AC electrical circuits. Calculate power consumption and estimate energy costs based on current, voltage, and power factor.
Enter the current in amperes
Common voltages: 120V (US household), 240V (US appliances), 230V (EU)
Most household circuits are AC Single Phase
Optional: Default 0.9 for AC. Range: 0-1 (1 = ideal)
How do I convert amps to watts?
For DC or AC single phase: Watts = Amps × Volts. Example: 10A × 120V = 1200W. For AC with power factor: Watts = Amps × Volts × Power Factor. Example: 10A × 120V × 0.9 = 1080W. For AC three phase: Watts = √3 × Amps × Volts × Power Factor. The power factor accounts for efficiency losses in AC circuits. Always use power factor for AC calculations to get accurate real power (not just apparent power).
What appliances use different amp ratings?
Common appliance amp ratings: Low draw (< 1A): LED lights, phone chargers, clocks. Light draw (1-5A): laptops, TVs, fans, small kitchen appliances. Medium draw (5-12A): vacuum cleaners, irons, coffee makers, microwaves. High draw (12-20A): hair dryers, space heaters, window AC units, power tools. Very high draw (> 20A, 240V): electric ranges (30-50A), dryers (24-30A), central AC (15-60A), electric water heaters (18-25A). Check device nameplate for exact ratings.
What is power factor and how does it affect wattage?
Power factor (PF) is the efficiency ratio in AC circuits, measuring how much current actually does work. PF = Real Power (Watts) / Apparent Power (VA). Range: 0 to 1. Typical values: Resistive loads (heaters, bulbs): PF ≈ 1.0 (100% efficient). Motors and compressors: PF ≈ 0.6-0.85. Power supplies and electronics: PF ≈ 0.5-0.95. LED drivers: PF ≈ 0.5-0.9. Impact: 10A at 120V with PF=1.0 = 1200W. Same 10A with PF=0.8 = 960W (240W wasted as reactive power). Higher PF = more efficient, lower electricity bills.
How much power can I safely use on a circuit?
Safe power limits by circuit breaker (continuous use, 80% rule): 15A breaker at 120V: max 1440W (12A × 120V). 20A breaker at 120V: max 1920W (16A × 120V). 30A breaker at 240V: max 5760W (24A × 240V). 50A breaker at 240V: max 9600W (40A × 240V). Exceeding causes: breaker tripping, wire overheating, fire risk. For motor startup or intermittent use, can briefly exceed but not continuously. Always leave 20% headroom for safety and surge protection.
What is the difference between watts and volt-amps?
Watts vs Volt-Amps (VA): Watts (W): Real power doing actual work (heating, mechanical work, light). Formula: W = V × A × PF. Volt-Amps (VA): Apparent power (total power including reactive). Formula: VA = V × A. Relationship: Watts = VA × Power Factor. Example: 10A × 120V = 1200VA. With PF=0.8: 1200VA × 0.8 = 960W. Utility bills charge for watts (real power). Circuit breakers rate by amps (protect based on current). UPS systems rate by VA (total capacity). For DC: Watts = VA always (PF=1).
How do I calculate three-phase power?
Three-phase power calculation: Watts = √3 × Volts × Amps × Power Factor. √3 ≈ 1.732. Example: 10A at 208V three-phase with PF=0.85: W = 1.732 × 208 × 10 × 0.85 = 3063W. Three-phase advantages: More efficient power delivery. Smaller wire for same power. Smoother power (motors run better). Common in: industrial facilities, large motors, commercial buildings. Voltages: 208V (common commercial), 480V (industrial), 240V (some residential). Verify voltage line-to-line vs line-to-neutral.
What are common electrical power examples by wattage?
Power consumption examples: Tiny (< 10W): LED bulb (8W), phone charger (5W). Small (10-100W): laptop (50W), ceiling fan (75W), TV (100W). Medium (100-500W): desktop computer (300W), refrigerator (150-400W). Large (500-1500W): microwave (1000W), vacuum (1200W), space heater (1500W). Very large (1500W+, often 240V): hair dryer (1800W), electric stove (3000W per element), dryer (5400W), central AC (3500-5000W), water heater (4500W), electric car charger (7200-19200W). Monthly cost = (Watts × Hours/day × Days × $0.12/kWh) ÷ 1000.