Watts to Amps Calculator

How to Convert Watts to Amps

Converting watts (power) to amps (current) requires knowledge of the voltage and the type of electrical system:

DC Circuits

For DC (Direct Current) circuits, the calculation is straightforward:

Example: For a 100-watt device connected to a 12-volt DC system:
Amps = 100W ÷ 12V = 8.33A

Single-Phase AC Circuits

For single-phase AC (Alternating Current) circuits, the power factor must be considered:

Example: For a 1000-watt device connected to 120-volt AC with a power factor of 0.9:
Amps = 1000W ÷ (120V × 0.9) = 9.26A

Three-Phase AC Circuits

For three-phase AC circuits, the calculation includes voltage, power factor, and the square root of 3:

Example: For a 10,000-watt device connected to a 208-volt three-phase system with a power factor of 0.85:
Amps = 10,000W ÷ (208V × 0.85 × 1.732) = 32.85A

Watts to Amps Conversion Table

Here are some common conversions for quick reference (assuming a power factor of 1.0):

At 120V (Common Household Voltage in US/Canada)

At 230V (Common Household Voltage in Europe/Asia)

Understanding Power Factor

Power factor is an important concept in AC electrical systems. It's a value between 0 and 1 that represents the ratio of real power (that performs work) to apparent power (total power in the circuit).

• Power Factor = 1.0: Ideal condition where all power is used efficiently
• Power Factor < 1.0: Some power is wasted due to inductive or capacitive loads

Common power factor values:

• 0.95-1.0: Electronic equipment with power factor correction
• 0.8-0.9: Motors and fluorescent lighting with ballasts
• 0.5-0.7: Heavily inductive loads like unloaded motors

A lower power factor means higher current is needed to deliver the same actual power, resulting in greater energy losses and potentially higher utility bills for commercial and industrial users.

Practical Applications

The watts to amps conversion is useful for many practical applications:

• Circuit design: Determining required wire gauge and circuit breaker size
• Load planning: Ensuring electrical panels can handle connected devices
• Appliance installation: Verifying if existing circuits can handle new appliances
• Generator sizing: Calculating the amp rating needed for a given power requirement
• Solar system design: Converting panel wattage to current for proper inverter sizing

Common Mistakes to Avoid

• Ignoring circuit type: Make sure to use the correct formula for DC, single-phase AC, or three-phase AC
• Forgetting power factor: In AC circuits, power factor significantly affects current draw
• Using peak power instead of continuous: Many devices have higher startup power than running power
• Not accounting for efficiency: Devices with lower efficiency require more input power