Ohm's Law Calculator
Enter any 2 of Voltage, Current, Resistance, or Power and solve for the other 2 — the full P/V/I/R power wheel.
Ohm's Law measurements
Enter your values, then calculate.
Enter any 2 of the 4 values below, leave the rest blank, then select Calculate.
Result
How to calculate ohm's law
Ohm's Law describes the fundamental relationship between voltage, current, and resistance in an electrical circuit — and combined with the power formula, lets you solve for any two unknown values when you know the other two.
How the calculation works
V = I × R (Ohm's Law), and P = V × I (Power formula). Together these four values (Voltage, Current, Resistance, Power) are all interrelated: knowing any two lets you solve for the remaining two.
Example
A 12V circuit drawing 2A: Resistance = V ÷ I = 12 ÷ 2 = 6Ω, and Power = V × I = 12 × 2 = 24W.
Frequently asked questions
What are the four values in Ohm's Law and the power formula?
Voltage (V, in volts) is electrical pressure, Current (I, in amps) is the flow of electric charge, Resistance (R, in ohms) is opposition to that flow, and Power (P, in watts) is the rate of energy use. Any two of these four values let you solve for the other two using V=IR and P=VI.
Ohm's Law Calculator
V = I × R (Ohm's Law), and P = V × I (Power formula). Together these four values (Voltage, Current, Resistance, Power) are all interrelated: knowing any two lets you solve for the remaining two.
Let's understand your ohm's law result.
Calculate a result above and this guide will help you interpret it using this calculator's own formula and explanation.
Pro Tips for Ohm's Law
- This is the single most foundational relationship in basic electrical circuits — understanding it makes most other electrical calculations easier to reason through.
- Enter any two known values (not just voltage and current) — the calculator can solve from any valid pair, including power combined with any other single value.
Common Ohm's Law Mistakes to Avoid
- Trying to enter three or more values at once expecting a more 'accurate' answer — the calculator needs exactly two known values to solve for the other two; entering more can create contradictions if they aren't mutually consistent.
When to Use This Calculator
Ohm's Law describes the fundamental relationship between voltage, current, and resistance in an electrical circuit — and combined with the power formula, lets you solve for any two unknown values when you know the other two.