Calculator KB-09
Ohm’s law calculator
Basic calculation for any DC circuit. Fill in two of the four fields.
Result
In brief: Online Ohm’s law calculator: calculate voltage, current, resistance, and power from any two known values, with a circuit diagram. Example: Resistance and power: 6 Ω · 24 W.
Calculation example
| Voltage U | 12 V |
|---|---|
| Current I | 2 A |
| Resistance and power | 6 Ω · 24 W |
|---|---|
| Voltage | 12 V |
| Current | 2 A |
| Resistance | 6 Ω |
| Power | 24 W |
How it is calculated
P = U · I = I² · R = U² / R
Ohm’s law relates voltage, current, and resistance, while power shows how much energy is converted into heat or work each second. Given any two values, you can calculate the others by direct substitution.
What to look for
- Choose a resistor with at least twice the required power rating: at its limit, it gets very hot and its resistance drifts from the rated value.
- The law applies to linear components. The resistance of an incandescent bulb, LED, or diode depends on current and temperature.
Frequently asked questions
How do I calculate current from voltage and resistance?
Divide voltage by resistance: I = U / R. At 12 V and 6 Ω, the current is 2 A and the power is 24 W.
How do I calculate resistance from voltage and power?
R = U² / P. A 230 V, 1000 W heater has a resistance of about 52.9 Ω when operating.
Why doesn’t Ohm’s law work for an LED?
A diode’s resistance depends on the current, and the relationship is nonlinear. That’s why you set the current with a resistor, then use Ohm’s law to calculate the resistor itself.
