LED Series Resistor Calculator LED Tool

Calculate current-limiting resistor for LEDs | Single or multiple LEDs in series

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mA
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šŸ“– LED Series Resistor Calculator

An LED series resistor (also called current-limiting resistor) is essential to prevent the LED from drawing too much current and burning out. This calculator determines the correct resistor value, power rating, and color code for your LED circuit.

šŸ“ LED Resistor Formula

R = (Vs - Vf Ɨ N) / I
Where:
R = Resistor value (Ī©)
Vs = Supply voltage (V)
Vf = LED forward voltage (V)
N = Number of LEDs in series
I = LED current (A)
Power: P = IĀ² Ɨ R (Watts)

šŸ“Š Common LED Forward Voltages

LED ColorForward Voltage (Vf)Typical Current
šŸ”“ Red1.8 - 2.0 V20 mA
šŸŸ” Yellow2.0 - 2.2 V20 mA
šŸŸ¢ Green2.0 - 2.2 V20 mA
šŸŸ  Orange2.0 - 2.2 V20 mA
šŸ”µ Blue2.4 - 3.0 V20 mA
āšŖ White3.0 - 3.4 V20 mA
šŸŸ£ UV3.2 - 3.6 V20 mA

ā“ Frequently Asked Questions

Why do LEDs need a resistor? ā–¼
LEDs have very low internal resistance and will draw excessive current if connected directly to a voltage source. A current-limiting resistor limits the current to a safe level, preventing the LED from burning out.
How do I choose the right resistor for my LED? ā–¼
Use the formula: R = (Vs - Vf Ɨ N) / I. For example, a red LED (1.8V) on 5V at 20mA needs R = (5 - 1.8) / 0.02 = 160Ī©. Use a standard value like 150Ī© or 180Ī©.
Can I connect multiple LEDs in series? ā–¼
Yes! The total forward voltage is the sum of all LED forward voltages. The supply voltage must be greater than the total Vf. Our calculator supports multiple LEDs in series.
What happens if I use a resistor with too low resistance? ā–¼
Too low resistance = too much current = LED burns out quickly. Always use a resistor that limits current to the LED's maximum rating (typically 20mA for standard LEDs).