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`.
Related Tools
Ohms Law Calculator
Calculate voltage, current, resistance, and power from any two known values.
Resistor Color Code Calculator
Calculate 4-band resistor value and tolerance from colors.
Voltage Divider Calculator
Calculate voltage divider output from Vin, R1, and R2.
Series and Parallel Resistor Calculator
Calculate the equivalent resistance of multiple resistors connected in series or parallel.
Battery Life Calculator
Estimate battery runtime from capacity and current draw.
Unit Converter
Convert units across 12 categories: length, mass, temperature, area, volume, speed, time, data storage, pressure, energy, power, and angle.