How the Ohm law calculator works
Choose which quantity you want to find, voltage, current, or resistance, then enter the other two, and the tool solves Ohm law for you. It also calculates electrical power. Ohm law states that voltage equals current times resistance, the single most useful relationship in basic electronics.
The Ohm law triangle
Voltage equals current times resistance, written V equals I times R. Rearranged, current is voltage divided by resistance, and resistance is voltage divided by current. Many people picture a triangle with V on top and I and R beneath: cover the unknown to see whether you multiply or divide.
Adding power to the picture
Electrical power in watts is voltage times current, P equals V times I. Combined with Ohm law you can also write power as current squared times resistance, or voltage squared divided by resistance. The tool reports power alongside your result so you can size resistors, supplies, and wiring safely.
Practical uses
Use it to choose a resistor for an LED, work out the current a device will draw, check whether a component will overheat, or understand a circuit on a schematic. Always respect component power ratings: a resistor that sees more watts than its rating will run hot and may fail.
Frequently asked questions
What is Ohm law? Voltage equals current times resistance; rearrange it to solve for any one of the three.
How do I calculate power? Multiply voltage by current; the tool shows watts automatically.
How do I find current from voltage and resistance? Divide voltage by resistance.
Related calculators: Density, Force, Kinetic Energy.