Free Ohms Law Calculator Online
Use this free Ohms Law calculator to find voltage, current, resistance, and power from any two known values. Ohms Law states that V = I x R, and this tool extends the formula to calculate power (P = V x I) as well. Enter any two quantities and see all four results instantly.
Enter any two values to calculate the other two.
Ohms Law Results
Enter any two values
How This Ohms Law Calculator Works
Ohms Law is the foundation of electrical engineering. The relationship V = I x R means that voltage equals current times resistance. When you know any two of the four electrical quantities (voltage, current, resistance, power), the Ohms Law calculator derives the other two using these formulas.
Practical example: a 12V battery powers a device that draws 3A. The Ohms Law calculator tells you the load resistance is 4 ohms and the power consumption is 36W. This is essential for sizing components, selecting fuses, and designing circuits.
Whether you are a student learning electronics, a hobbyist building projects, or an electrician sizing circuits, the Ohms Law calculator gives you fast, reliable results without manual formula rearrangement.
Ohms Law Formula Wheel
The Ohms Law calculator uses these core formulas plus derived variants like P = I^2 x R and P = V^2 / R.
Understanding Electrical Units
Volts (V)
Voltage is the electrical pressure that drives current through a circuit. Household outlets provide 120V in the US and 230V in Europe. Higher voltage pushes more current through the same resistance.
Amps (A)
Current is the rate at which electrons flow through a conductor. A typical household circuit is rated at 15A or 20A. The Ohms Law calculator helps verify that current stays within safe limits.
Ohms and Watts
Resistance (ohms) opposes current flow, while power (watts) measures energy conversion rate. A 100W bulb on a 120V circuit draws 0.83A and has 144 ohms resistance — all derivable from Ohms Law.
Frequently Asked Questions
Disclaimer: This Ohms Law calculator is for educational purposes only. Always verify calculations with professional tools and consult a qualified electrician for circuit design and safety-critical applications.