Ohms Law Calculator
Calculate voltage, current, resistance, or power using Ohms Law and the power equation.
An Ohm's Law calculator finds voltage, current, resistance, or power from any two known electrical values using V = IR and P = VI.
Examples
Find voltage: 2A through 50 ohms
Find resistance: 120V, 60W bulb
Frequently Asked Questions
What is Ohm's Law?
Can I use this for AC circuits?
Quick Tips
- •Remember the Ohm's Law wheel: V = IR, I = V/R, R = V/I, P = VI, P = I²R, P = V²/R.
- •Double-check your units — voltage in volts, current in amps, resistance in ohms, power in watts.
An Ohm's Law calculator finds voltage, current, resistance, or power from any two known electrical values using V = IR and P = VI.
How to Use This Calculator
Select which value you want to solve for, then enter at least two of the remaining known values. The calculator uses Ohm's Law and the power equations to find all four values.
Understanding the Formula
V = I x R (Ohm's Law). P = V x I. P = I^2 x R. P = V^2 / R. Any two known values can determine the other two.
Examples
Find voltage: 2A through 50 ohms
V = I x R = 2 x 50 = 100 V. Power: P = V x I = 100 x 2 = 200 W.
Find resistance: 120V, 60W bulb
R = V^2 / P = 120^2 / 60 = 240 ohms. Current: I = P / V = 60 / 120 = 0.5 A.
Frequently Asked Questions
What is Ohm's Law?
Ohm's Law states that the voltage across a conductor is directly proportional to the current flowing through it, with resistance as the proportionality constant: V = I x R.
Can I use this for AC circuits?
This calculator handles DC circuits and purely resistive AC circuits. For AC circuits with capacitance or inductance, impedance (Z) replaces resistance and calculations become more complex.
Assumptions & Limitations
- Applies to DC circuits and purely resistive AC circuits only.
- Assumes ideal conductors with no temperature-dependent resistance changes.
- Does not account for impedance from capacitance or inductance in AC circuits.