Ohm's Law Calculator
Enter any 2 values — the third will be calculated
Ohm's Law states that the voltage across a conductor is proportional to the current flowing through it, with resistance as the proportionality constant: V = IR. Formulated by Georg Ohm in 1827, it is the most fundamental relationship in electrical engineering. It applies to ohmic materials at constant temperature; real-world components like diodes and transistors are non-ohmic.
- 1V = IR (voltage = current × resistance)
- 2I = V/R (current = voltage / resistance)
- 3R = V/I (resistance = voltage / current)
- 4Power: P = VI = I²R = V²/R
- 5Units: V (volts), A (amperes), Ω (ohms), W (watts)
12 V battery, 6 Ω resistor=I = 12/6 = 2 A, P = 12 × 2 = 24 W
230 V mains, 60 W bulb=R = 230²/60 = 882 Ω, I = 60/230 = 0.26 A
| Find | Formula | Notes |
|---|---|---|
| Voltage V | V = I × R | |
| Current I | I = V / R | |
| Resistance R | R = V / I | |
| Power P | P = V × I = I²R = V²/R | Power triangle |
| Energy E | E = P × t | Joules = Watts × seconds |
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