LED Resistor Calculator
Calculate the correct resistor value for your LED circuit to prevent damage and ensure optimal brightness.
Circuit Parameters
V
V
Typical: Red (1.8-2.2V), Yellow (2.0-2.4V), Green (2.2-3.4V), Blue/White (3.0-3.6V)
mA
Typical: 5-20mA for standard LEDs, 20-30mA for high-brightness LEDs
Series: LEDs share one resistor. Parallel: Each LED needs its own resistor (or one for all).
Calculation Results
Calculated Resistor Value
500.00 Ω
Nearest Standard Resistor
470 Ω
E24 series standard value
Power Dissipation
0.200 W
Use a resistor rated for at least 1W (2x safety margin)
Actual Current (with standard resistor)
21.28 mA
Within acceptable range
Resistor Tolerance Range
Min: 475.00 Ω
Max: 525.00 Ω
Formula Used
R = (Vs - n × Vf) / If
Where: Vs = 12V, n = 1, Vf = 2.0V, If = 20mA
Important Notes
- Always use a resistor rated for at least 2x the calculated power dissipation for safety.
- For parallel LEDs, it's recommended to use one resistor per LED for better current matching.
- Standard LED forward voltages: Red (1.8-2.2V), Yellow (2.0-2.4V), Green (2.2-3.4V), Blue/White (3.0-3.6V).
- If the calculated resistor value is negative, increase the supply voltage or reduce the number of LEDs.