💡 LED Series Resistor Calculator
Calculate the resistor value needed to safely power your LEDs. Avoid burnout and ensure long life.
💡 Expert Tips
Always round UP. If the calculated resistance is 143Ω, don't use 140Ω. Use 150Ω. A slightly higher resistance just makes the LED slightly dimmer (barely noticeable), but a lower resistance can drastically reduce its lifespan.
Check the Power Rating! Most small resistors are rated for 1/4 Watt (0.25W). If your calculation says the resistor dissipates 0.5W, a standard resistor will get extremely hot and fail. Use a 1W resistor instead.
Connecting LEDs in Series? If you have 3 Red LEDs (2V each) in series, your total Vf is 6V. You need a source voltage higher than 6V (like 9V or 12V) to light them up. The calculation is R = (Vs - Total_Vf) / If.
"I've blown up my fair share of LEDs by 'just testing' them on a 9V battery. Don't be like me. This calculator takes 5 seconds to use and saves you from the smell of burnt electronics."