Calculate voltage, current or resistance using Ohm's law. Fill in two of the three fields and leave the third at 0, and the calculator works out the rest.
Ohm's law states that the voltage (V) across a conductor equals the current (I) through it multiplied by its resistance (R). Voltage is measured in volts (V), current in amperes (A), and resistance in ohms (Ω).
If you know two of the three values, you can solve the equation for the third: R = V ÷ I to find resistance, or I = V ÷ R to find current.
Ohm's law describes the relationship between voltage, current and resistance in an electrical circuit: the voltage across a conductor equals the current through it multiplied by its resistance (V = I × R). The law is one of the cornerstones of electrical engineering.
Resistance is measured in ohms (Ω), named after Georg Simon Ohm. One ohm is defined as the resistance that produces a current of one ampere when the voltage across the conductor is one volt.
Ohm's law gives you voltage, current and resistance, but to find power (and therefore energy consumption) you also need P = U × I. See a power calculator to work out watts and kilowatt-hours from voltage and current.