Electrical Power
P = V × I
Quick answer
This calculator solves P = V × I = I²R = V²/R for Power. With Voltage 12 V, Current 2 A, Resistance 0.47 kΩ, the result is 24 W. It solves in 4 directions, so you can enter the values you have and get the one you need.
Calculator
Formula
Description
Electrical power measures the rate at which electrical energy is converted into another form such as heat, light, or motion. The three equivalent forms are derived by substituting Ohm's Law into the base formula P = VI. The I²R form is particularly useful for calculating resistive heating losses in wires and components, known as Joule heating or I-squared-R losses. The V²/R form is convenient when voltage is fixed and you want to find how power changes with resistance, such as in power supply loading scenarios.
Variables
- P — Power in watts (W), the rate of energy transfer
- V — Voltage in volts (V)
- I — Current in amperes (A)
- R — Resistance in ohms (Ω)
Practical Notes
Power ratings on resistors indicate the maximum continuous dissipation before damage. Always derate by 50% or more for reliability. In AC circuits, this formula gives apparent power; real power requires multiplying by the power factor.
Symbols and units
| Symbol | Meaning | Default unit | Accepted units |
|---|---|---|---|
| P | Power | W | µW, mW, W, kW |
| V | Voltage | V | pV, nV, µV, mV, V, kV |
| I | Current | A | pA, nA, µA, mA, A, kA |
| R | Resistance | Ω | mΩ, Ω, kΩ, MΩ |
Step by step
- 1. What you know: Voltage 12 V, Current 2 A, Resistance 0.47 kΩ
- 2. The relation: P = V × I = I²R = V²/R
- 3. Substitute: V = 12 V, I = 2 A, R = 0.47 kΩ
- 4. Result: Power = 24 W
Related quantities from the same inputs
- P = V × I = 24 W
Worked examples
Minimum range
Given: Voltage 0.33 V, Current 2 mA, Resistance 1 Ω
Result: Power = 0.66 mW
Low range
Given: Voltage 3.3 V, Current 20 mA, Resistance 10 Ω
Result: Power = 66 mW
Typical
Given: Voltage 12 V, Current 2 A, Resistance 0.47 kΩ
Result: Power = 24 W
High range
Given: Voltage 0.23 kV, Current 100 A, Resistance 4.7 kΩ
Result: Power = 23 kW
Maximum range
Given: Voltage 2.3 kV, Current 1 kA, Resistance 47 kΩ
Result: Power = 2300 kW
Solving for each variable
Solve for Power
Voltage 0.33 V, Current 2 mA, Resistance 1 Ω → 0.66 mW
Solve for Voltage
Power 10 mW, Current 2 mA, Resistance 1 Ω → 100 mV
Solve for Current
Power 10 mW, Voltage 0.33 V, Resistance 1 Ω → 100 mA
Solve for Resistance
Power 10 mW, Voltage 0.33 V, Current 2 mA → 2.5 kΩ
How Power changes with Voltage
| Voltage (input) | Power (result) |
|---|---|
| 1.2 V | 2.4 W |
| 3 V | 6 W |
| 6 V | 12 W |
| 9 V | 18 W |
| 12 V | 24 W |
| 18 V | 36 W |
| 24 V | 48 W |
| 48 V | 96 W |
| 84 V | 0.168 kW |
| 120 V | 0.24 kW |
The same result in other units
| Unit | Value |
|---|---|
| mW | 24000 |
| W | 24 |
| kW | 0.024 |
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<p><a href="https://vbatpower.com/formulas/power/">Electrical Power</a> Calculator by vbatpower.com</p>Frequently asked questions
How do you calculate Electrical Power?
Use P = V × I = I²R = V²/R. With Voltage 12 V, Current 2 A, Resistance 0.47 kΩ, Power works out to 24 W.
How do you calculate s q e p electrical power?
Rearrange for Power: with Voltage 3.3 V, Current 20 mA, Resistance 10 Ω, Power is 66 mW.
What is the formula for Electrical Power?
The formula is P = V × I = I²R = V²/R. Electrical power measures the rate at which electrical energy is converted into another form such as heat, light, or motion.
How do you find Voltage when you know the other values?
Rearrange for Voltage: with Power 10 mW, Current 2 mA, Resistance 1 Ω, Voltage is 100 mV.
How do you find Current when you know the other values?
Rearrange for Current: with Power 10 mW, Voltage 0.33 V, Resistance 1 Ω, Current is 100 mA.
What units does Electrical Power use?
Power is shown in mW, W, kW. Values are held in SI base units internally, so you can mix prefixes without converting by hand.
Related Concepts
All Basic Electronics formulas →Need more features?
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