Ohm's law calculator
Enter two of voltage, current, resistance and power to get the other two, by Ohm's law and the power formula.
22.7 mA · 114 mW
- Voltage
- 5 V
- Current
- 22.7 mA
- Resistance
- 220 Ω
- Power
- 114 mW
The formulas
| To find | Formula |
|---|---|
| Voltage (V) | V = I × R |
| Current (I) | I = V ÷ R |
| Resistance (R) | R = V ÷ I |
| Power (P) | P = V × I = I² × R = V² ÷ R |
An example
A 220 Ω resistor on an Arduino's 5 V carries I = 5 ÷ 220 = 0.0227 A, that is 22.7 mA. It takes P = 5 × 0.0227 = 0.114 W, so an ordinary 1/4 W resistor will do. Current is entered in milliamps (mA): 1 A = 1000 mA. Resistance can be written as 4.7k or 1M. For the resistor in front of an LED: the LED resistor calculator
In the app, tick off every wire, match the parts to your inventory and pick up where you left off.
