Hardware tool
LED Resistor Calculator
Calculate a safe series resistor, resistor power, and standard value for one or more LEDs.
Runs in your browserResult
- LED string voltage
- 6.6 V
- Voltage across resistor
- 5.4 V
- Calculated resistance
- 270 Ω
- Next E12 value
- 270 Ω
- Resistor dissipation
- 0.108 W
- Suggested resistor rating
- 0.25 W
Confirm the LED datasheet, maximum current, forward-voltage range, resistor tolerance, temperature, and supply variation. High-power LEDs need regulated drivers.
How to use this led resistor calculator
- Enter the known electrical values with the correct units, then check the proposed current, voltage, resistance, or wire result.
- Review the calculated totals, units, and assumptions. Check the inputs and units before relying on the result.
- Change one input at a time to compare another case, then copy or save the result you plan to use.
About this led resistor calculator
Use the LED Resistor Calculator to calculate a safe series resistor, resistor power, and standard value for one or more LEDs. The result changes when you adjust the values or options above.
You can also use it to compare results after changing one input.
Example
For a 5-volt supply and a 2-volt LED at 20 mA, calculate the series resistance and choose a standard resistor with enough power rating.
Common uses
- → calculate a safe series resistor, resistor power, and standard value for one or more LEDs
- → compare results after changing one input
- → save an estimate for planning or comparison