Micro Tools
Advertisement

Ohms Law Calculator

Solve any Ohms law circuit: enter two values and get voltage, current, resistance and power instantly.

Ohms law

Pick what to solve for, then enter the two known values.

Voltage
-

Enter two values to solve the circuit.

Advertisement

The two Ohms law formulas

Voltage equals current times resistance, V = I x R. Power equals voltage times current, P = V x I, which also gives P = I squared x R. From these two relationships you can solve for any one of the four values when you know two others.

Why power matters too

Knowing the power tells you how much heat a component must handle. A resistor dropping 12 volts at 1 amp dissipates 12 watts, so a small quarter watt resistor would burn out. The calculator always shows power alongside the solved value.

Related tools

Mortgage calculatorMonthly cost with taxes, insurance, PMI and payoff schedule. Loan calculatorMonthly payment and interest for auto and personal loans. Compound interestSee how savings grow with compound interest.

Ohms Law Calc FAQs

What is Ohms law in simple terms?
Voltage pushes current through resistance. Double the voltage and current doubles; double the resistance and current halves. The calculator applies V = I x R instantly.
How do I find current if I know voltage and resistance?
Divide voltage by resistance: I = V / R. A 12 volt supply across 4 ohms gives 3 amps. Select Current in the solve for menu and enter 12 and 4.
How do I calculate power in watts?
Multiply voltage by current: P = V x I. A 12 volt, 3 amp load uses 36 watts. The calculator shows power for every solve mode.
Can resistance be zero in the calculator?
No, zero resistance means a short circuit with theoretically infinite current, so the calculator blocks it. Real wires have small but nonzero resistance.
What units does the calculator use?
Volts, amps, ohms and watts. For milliamps, enter decimals: 20 mA is 0.02 A. For kilo ohms, enter thousands: 4.7k is 4700.
Advertisement