Ohm's Law Calculator
Find voltage, current, resistance or power
Solve any Ohm's law problem instantly. Enter any two known values — voltage, current or resistance — and get the third value plus power, calculated automatically using V = IR.
Calculate now — free
Free Ohm's Law Calculator — Find Voltage, Current, Resistance & Power
Ohm's law is one of the first formulas students meet in physics and electronics: V = IR, where voltage (V) equals current (I) multiplied by resistance (R). Rearranging the formula to solve for current or resistance is a step that trips up a lot of students under exam pressure. This Ohm's law calculator handles the rearrangement for you — pick which quantity you're solving for, enter the other two known values, and get an instant, accurate result.
Alongside voltage, current and resistance, the calculator also works out power (P) automatically using P = VI (or the equivalent P = I²R), so you get a complete picture of the circuit from just two known values — no separate power calculation needed.
Every result uses the standard formulas taught in TN Board, CBSE, NEET and JEE physics syllabi, so what you see here matches what's expected in exam answers. That makes this tool useful beyond just checking homework: verifying a circuit calculation, working through electronics coursework, or double-checking a numerical before an exam.
Just choose what you're solving for, type in the two values you already know, and the result updates instantly — no "calculate" button to click, no page reload, no waiting.
← Back to all unit convertersOhm's law — common questions
Ohm's law states that the voltage across a conductor is directly proportional to the current flowing through it, given constant resistance: V = IR, where V is voltage in volts, I is current in amps, and R is resistance in ohms.
Rearrange V = IR to I = V ÷ R. For example, if V = 10 volts and R = 5 ohms, then I = 10 ÷ 5 = 2 amps.
Rearrange V = IR to R = V ÷ I. For example, if V = 10 volts and I = 2 amps, then R = 10 ÷ 2 = 5 ohms.
Multiply voltage by current: P = VI. For example, 10 volts × 2 amps = 20 watts.
Yes, using P = I²R. For example, with I = 2 amps and R = 5 ohms, P = 2² × 5 = 20 watts — the same result as P = VI.
Yes — it uses the standard Ohm's law formulas taught in TN Board, CBSE, NEET and JEE physics syllabi, so results match what's expected in exam answers.