LED resistor
Calculate the current-limiting resistor for an LED from supply voltage, forward voltage and LED current. Also returns the standard E12 value.
Inputs
e.g. 5 V on Arduino, 3.3 V on ESP32.
Result
How it works
Why an LED needs a resistor
An LED barely limits its own current: wired straight to the supply it draws too much and burns out. A series resistor holds the current at a safe value (typically 20 mA).
The E12 value
The ideal value rarely exists in stores. We round up to the nearest standard E12 value — a bit more resistance means a bit less current, which is safe for the LED.
Formula
R = (V_fonte − V_led) / I_ledMore in Electronics
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