Power, Energy & Ohm's Law Calculator
Convert power and energy units, or solve Ohm's law, power, and energy relationships.
How the Power, Energy & Electrical works
Power units convert through the watt and energy units through the joule. One kilowatt-hour is 3.6 million joules, and mechanical horsepower is about 745.7 W.
The Ohm's law calculator takes any two of voltage, current and resistance, solves for the third and derives power, showing each step of the working.
Formulas used
- Ohm's law
V = I × R- Electrical power
P = V × I = I² × R = V² ÷ R- Energy
E (kWh) = P (kW) × t (h)
How to use the Power, Energy & Electrical in 3 steps
Step 1
Choose the power converter, energy converter or Ohm's law calculator.
Step 2
Enter your known values, such as watts to convert or any two of V, I and R.
Step 3
Read the converted value or the solved quantity together with its formula.
Frequently asked questions
How many watts are in one horsepower?
One mechanical horsepower is about 745.7 watts; one metric horsepower is about 735.5 watts.
How do I calculate current from power and voltage?
Divide power by voltage: I = P ÷ V. A 1,200 W heater on 240 V draws 5 A.