LED RESISTORS CALCULATOR
LED Resistor Calculator
(Red ≈ 2.0V, Green/Blue ≈ 3.2V)
Power Dissipation: 0.06 W
| LED Color | Typical Voltage Drop (Vled) |
| Red | 1.8V – 2.2V |
| Yellow / Orange | 2.0V – 2.4V |
| Green | 3.0V – 3.4V |
| Blue / White | 3.0V – 3.6V |
How to Choose a Resistor for Your LED
Unlike a light bulb, an LED (Light Emitting Diode) is a current-dependent device. If you connect it directly to a power source, it will draw too much current and burn out instantly. A current-limiting resistor is essential to keep the current at a safe level.
The Calculation Formula
To find the correct resistance value, we use a variation of Ohm’s Law:
Vsource: Your power supply (e.g., 5V or 3.3V).
Vf: Forward voltage of the LED (color-dependent).
Iled: Desired current in Amperes (e.g., 0.02A for 20mA).
Power Rating Matters
Don’t forget the power dissipation! The resistor converts excess voltage into heat. Calculate the power using P=(Vsource−Vled)×Iled. If the result is 0.1W, a standard 0.25W (1/4 Watt) resistor will work perfectly. If it’s higher, you may need a beefier power resistor.