LED Resistor Calculator
Calculate the perfect resistor value to protect your LEDs
Input Parameters
V
V
mA
Calculation Results
Required Resistor Value
350 Ω
Standard Resistor: 330 Ω
Resistor Power Rating
0.14 W
Recommended: 1/4 W (0.25 W)
Safety Note: Always use a resistor with adequate power rating
Calculation Formula
The resistor value is calculated using Ohm's Law:
R = (Vsource - VLED) / ILED
Where:
- R: Required resistor value in ohms (Ω)
- Vsource: Voltage of the power supply in volts (V)
- VLED: Forward voltage of the LED in volts (V)
- ILED: Current through the LED in amperes (A)
Example Calculation
For a 9V power supply and a red LED that requires 2V to operate and consumes 20mA (0.02A) of current:
R = (9V - 2V) / 0.02A = 7V / 0.02A = 350Ω
In this case, you would use a 350Ω resistor or the closest standard value (330Ω).
5mm LED Specifications
Red LED
1.8V - 2.2V, 20mA
Yellow LED
2.0V - 2.2V, 20mA
Green LED
2.0V - 3.2V, 20mA
Blue LED
3.0V - 3.5V, 20mA
White LED
3.0V - 3.5V, 20mA
