Power Calculator
Calculate electrical power (watts), voltage (volts), current (amps), and resistance (ohms) using the power formula and Ohm's Law. Essential for electricians, students, and engineers.
Interactive Calculator Coming Soon
Use the formulas and reference tables below for manual calculations while the full tool is being built.
Core Electrical Formulas
Ohm's Law
V = I × R
Power (from V and I)
P = V × I
Power (from I and R)
P = I² × R
Power (from V and R)
P = V² / R
Current from P and V
I = P / V
Voltage from P and I
V = P / I
Common Appliance Power Reference
| Appliance | Typical Wattage |
|---|---|
| LED light bulb | 8 – 12 W |
| Laptop computer | 45 – 100 W |
| Desktop computer | 100 – 300 W |
| Microwave oven | 600 – 1,200 W |
| Electric kettle | 1,500 – 3,000 W |
| Hair dryer | 1,000 – 2,000 W |
| Air conditioner (1 ton) | 900 – 1,200 W |
| Electric vehicle charger (Level 2) | 7,200 – 11,500 W |
Frequently Asked Questions
What is Ohm's Law?▼
Ohm's Law states V = I × R. Voltage equals current multiplied by resistance. Knowing any two of these three values lets you calculate the third.
How do you calculate electrical power?▼
Electrical power (P) in watts = Voltage (V) × Current (I). You can also calculate it as P = I² × R or P = V² / R.
What is the difference between watts and kilowatts?▼
1 kilowatt (kW) = 1,000 watts (W). Energy bills are charged in kilowatt-hours (kWh) — the energy used by a 1,000W appliance running for 1 hour.