LED Resistor Calculator
Calculate the appropriate resistor value and power rating for LED circuits to ensure proper current limiting and voltage regulation.
How LED Resistor Calculator Works
Calculation Formulas
Series Connection:
Voltage Drop = Supply Voltage - (LED Voltage x Number of LEDs)
Resistance = Voltage Drop / LED Current
Power = Voltage Drop x Current
Parallel Connection:
Voltage Drop = Supply Voltage - LED Voltage
Total Current = LED Current x Number of LEDs
Resistance = Voltage Drop / Total Current
Power = Voltage Drop x Total Current
Common LED Specifications
| LED Color | Forward Voltage | Typical Current |
|---|---|---|
| Red | 1.8 - 2.2V | 20mA |
| Yellow/Orange | 1.8 - 2.2V | 20mA |
| Green | 2.0 - 2.4V | 20mA |
| Blue | 3.0 - 3.4V | 20mA |
| White | 3.0 - 3.4V | 20mA |
| UV/Purple | 3.2 - 3.8V | 20mA |
Design Tips
- Always use a current-limiting resistor with LEDs to prevent damage
- Choose resistor power rating at least 2x the calculated value for safety
- Use standard resistor values from E12 or E24 series
- For high-power LEDs, consider constant current drivers instead of resistors
- Check LED datasheet for exact forward voltage and maximum current specifications
- Series connection is more efficient but all LEDs fail if one fails
- Parallel connection allows individual LED control but requires more current
Standard Resistor Values (E12 Series)
Common resistor values available in most electronics stores:
1.0, 1.2, 1.5, 1.8, 2.2, 2.7, 3.3, 3.9, 4.7, 5.6, 6.8, 8.2 (and their multiples by 10, 100, 1000, etc.)
Cite this page as:
Daniel, P. LED Resistor Calculator. Available at: https://constructioncalculators.com/led-resistor-calculator/. Accessed: October 25, 2026.