💡
LED Resistor Calculator
Series resistor for one or more LEDs.
300 Ω
Resistor
300 Ω → 20 mA
Next E24 value (≥)
120 mW
Power in resistor
0.25 W
Recommended rating
Runs entirely in your browser. Nothing is sent anywhere.
How it works
- 1Enter your values.
- 2See the result update instantly as you type.
- 3Change any value to compare scenarios.
About this tool
LED Resistor Calculator: Series resistor for one or more LEDs. Type your numbers and the result is calculated instantly — no button to press, nothing to install. All math runs locally in your browser, so the values you enter are never sent anywhere.
Example
| Input | |
|---|---|
| Supply voltage (V) | 12 |
| LED forward voltage (V) | 2 |
| LED current (mA) | 20 |
| LEDs in series | 3 |
| Result | |
| Resistor | 300 Ω |
| Next E24 value (≥) | 300 Ω → 20 mA |
| Power in resistor | 120 mW |
| Recommended rating | 0.25 W |
How do I use the LED Resistor Calculator?
Enter your values. See the result update instantly as you type. Change any value to compare scenarios.
Is the LED Resistor Calculator free?
Yes. It is completely free with no sign-up, no usage limits and no watermark.
Is my data sent to a server?
No. Everything is calculated locally in your browser. Nothing you enter is uploaded, logged or stored.
Does it work on my phone?
Yes. It works in any modern browser on Android, iPhone, iPad, Windows, Mac and Linux — no app needed.