LED Resistor Calculator
Calculate the resistor value needed for LEDs based on supply voltage, forward voltage, and current. Essential for LED circuit design.
LED Resistor Calculator
Red: ~2.0V, Yellow: ~2.1V, Green: ~2.2V, Blue/White: ~3.0-3.4V
Typical: 20mA for standard LEDs, 350mA+ for high-power
Common LED Forward Voltages
| LED Color | Forward Voltage (V) | Typical Current (mA) | Notes |
|---|---|---|---|
| Red | 1.8 - 2.2 | 20 | Most common |
| Yellow | 2.0 - 2.4 | 20 | Similar to red |
| Green | 2.1 - 2.5 | 20 | Standard green |
| Blue | 3.0 - 3.4 | 20 | Higher voltage |
| White | 3.0 - 3.6 | 20-350 | Varies by type |
| UV (Ultraviolet) | 3.1 - 4.4 | 20 | Specialized |
| IR (Infrared) | 1.2 - 1.7 | 20-100 | Lowest voltage |
Formulas
Single LED:
R = (Vs - Vf) / I
Where: R = resistor (Ω), Vs = supply voltage (V), Vf = forward voltage (V), I = current (A)
LEDs in Series:
R = (Vs - (Vf × n)) / I
Where: n = number of LEDs (same current, voltages add)
LEDs in Parallel:
R = (Vs - Vf) / (I × n)
Where: n = number of LEDs (same voltage, currents add)
Power Dissipation:
P = I² × R = V × I
Where: P = power (W), V = voltage drop across resistor
Note: Always use a resistor rated for at least 2× the calculated power dissipation for safety. For series LEDs, ensure total forward voltage is less than supply voltage. For parallel LEDs, each LED should have its own resistor for best results.