offlinewebtools.com — free, watermark-free browser tools that stay on your device with nothing uploading to our servers

LED Resistor Calculator

Work out the perfect series resistor to protect LEDs. Enter your supply voltage, LED forward voltage, and desired current to calculate the ideal resistor value.

Free to use, no watermarks, runs in your browser—nothing uploads to our servers

Supply voltage (V)

LED forward voltage (V)

Desired LED current (mA)

Report a bug

If this tool misbehaves, share a quick summary so we can investigate. We include the tool URL automatically—no need to copy and paste.