Ohm's law calculator
Type any two of voltage, current and resistance and the third follows from V = IR. For 12 V and 0.5 A, R = 12 / 0.5 = 24 Ω, and the power is 6 W.
Ohm's law
V = IR at a fixed temperature. Pick what to find and type the other two. Add a time to get the heat, H = I²Rt, and the energy in kWh.
Resistance R24 Ω
Power6 W
- R = V / I = 12 / 0.5 = 24 Ω
- Power: P = VI = 12 × 0.5 = 6 W. The same as I²R and V²/R.
Why it works
- V = IR gives the voltage from the current and the resistance.
- I = V/R gives the current: more voltage pushes more current, more resistance lets less through.
- R = V/I gives the resistance from a reading of each meter.
- Power follows from any two of them: P = VI = I²R = V²/R.
- The heat in a time t is H = I²Rt, Joule's law of heating.
Ohm's law calculator: quick answers
What are the units in V = IR?
Volts, amperes and ohms. Convert milliamperes to amperes first: 250 mA is 0.25 A.
How do I find resistance from voltage and current?
Divide: R = V/I. For 12 V and 0.5 A that is 24 Ω.
How do I find the power as well?
Multiply the voltage by the current: P = VI = 12 × 0.5 = 6 W.