LED Resistor Calculator
Calculate current-limiting resistor for LED circuits
How to Use
- Select an LED preset or manually enter forward voltage and current
- Enter supply voltage
- Set the number of LEDs to connect in series (default 1)
- Required resistance and E24 standard resistor recommendation are displayed automatically
- Click the "Copy" button to copy calculation results to clipboard
Use Cases
- Choosing a resistor to light up LEDs in electronics projects
- Driving LEDs from Arduino or Raspberry Pi GPIO
- Designing circuits with multiple LEDs connected in series
- Checking if spare resistors can be used as substitutes
Frequently Asked Questions
What is the E24 standard resistor series? ▼
The E24 series is a standard resistor value series widely used in electronic components. Each decade has 24 defined values (1.0, 1.1, 1.2, ...9.1), and most commercially available resistors follow this series.
What is the difference between the recommended resistor and the nearest standard value? ▼
The nearest standard value is the E24 value closest to the calculated value. The recommended resistor is the next larger E24 value above the calculated value, which keeps current at or below the calculated value for safe LED protection.
What happens when connecting multiple LEDs in series? ▼
When you set the LED count, the total forward voltage (Vf × count) is automatically calculated. The resistor value is calculated based on the remaining voltage after subtracting the total Vf from the supply voltage. An error is displayed if the supply voltage is lower than the total Vf.
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