Free Online Tool
LED Resistor Calculator
Find the resistor value and resistor power dissipation from supply voltage, LED forward voltage, and LED current.
The result will appear here.
How to Use
- Enter supply voltage, LED forward voltage, and LED current.
- Click calculate.
- Check resistor value and power dissipation.
Examples
- Calculate resistance for 5V supply, 2V LED, and 20mA
- Check resistor wattage for an LED circuit
Calculation and Conversion Notes
The required series resistor is calculated as `R = (Vs - Vf) / If`. Here, `Vs` is the supply voltage, `Vf` is the LED forward voltage, and `If` is the LED current. Resistor power is calculated as `P = I^2 × R`.
FAQ
Does LED Resistor Calculator save my input?
No. Your input is not stored on a server. Supported actions run in your browser.
Can I use it on mobile?
Yes. The pages are responsive and work on desktop and mobile browsers.
Can I rely on the result?
Use the result as a quick reference. Important work should be checked separately.