Power Calculator
Calculate electrical power, current, or voltage from any two known quantities with automatic engineering-unit conversion. This tool supports supply sizing, load checks, and early hardware design calculations.
Engineering tool
Power Calculator
Calculate power, current, or voltage with engineering unit conversion.
Primary Result
24 W
Result console
- Power in milliwatts
- 24,000mW
- Power in watts
- 24W
- Power in kilowatts
- 0.024kW
- Voltage in millivolts
- 12,000mV
- Voltage in volts
- 12V
- Voltage in kilovolts
- 0.012kV
- Current in microamperes
- 2,000,000µA
- Current in milliamperes
- 2,000mA
- Current in amperes
- 2A
Formula: P = V × I
Scientific notation: 2.400000e+1 W
Interpretation: 12.0000 V at 2.00000 A represents 24.0000 W of electrical power.
Formula reference
Electrical Power Formulas
Use base SI units: volts, amperes, and watts.
Power: P = V × ICurrent: I = P / VVoltage: V = P / IVariable definitions
- P
- electrical power in watts
- V
- voltage in volts
- I
- current in amperes
Worked Examples
Engineering Notes
- Electrical power is the product of voltage and current.
- DC power calculations assume steady voltage and current.
- AC real power may require power factor.
- Power is useful for supply sizing, PCB trace checks, MOSFET loss, and fuse selection.
- Always include safety margin when sizing power supplies.
Support reference
FAQ
What is electrical power?
Electrical power is the rate of energy transfer. For steady DC circuits it equals voltage multiplied by current and is measured in watts.
How do I calculate current from power and voltage?
Divide power in watts by voltage in volts: I = P / V. The result is current in amperes.
How do I calculate voltage from power and current?
Divide power in watts by current in amperes: V = P / I.
Can this calculator be used for AC circuits?
It can estimate apparent power from RMS voltage and current. AC real power may also require power factor and phase information.
What units does this calculator support?
Voltage supports mV, V, and kV; current supports µA, mA, and A; power supports mW, W, and kW.
Documentation
Related Engineering Guides
Design notes, guides, and engineering articles linked to this tool.
Engineering Guide
Understanding Electrical Power
Learn electrical power fundamentals, including voltage, current, resistance, watts, energy, Ohm's law, DC and AC power, efficiency, power dissipation, and practical calculations.
18 min · Beginner
Engineering Blog
10 Common Power Design Mistakes (and How to Avoid Them)
Avoid power design mistakes involving watts versus watt-hours, unit prefixes, RMS current, AC power factor, efficiency, derating, thermal design, startup current, voltage drop, batteries, PCB copper, and undersized components.
17 min · Intermediate
Engineering Guide
Power Dissipation and Component Power Ratings
Calculate actual component dissipation and choose safe power ratings using thermal resistance, derating, junction temperature, SOA, pulse conditions, PCB heat spreading, and real operating conditions.
20 min · Intermediate
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