LED抵抗計算機

共有リンク

はじめに

LED Resistor Calculator — Series resistor value and power for any LED. Enter Supply voltage (V), LED forward voltage (V), LED current (mA) to get an instant, accurate result.

計算式

Resistance = (supply voltage − LED forward voltage) / LED current. Power = (supply − forward voltage) × current.

ステップごとの説明

Enter the Supply voltage (V).
Enter the LED forward voltage (V).
Enter the LED current (mA).
Click Calculate to see your result instantly.

実例

Example: With Supply voltage (V) = 9, LED forward voltage (V) = 2, LED current (mA) = 20, the LED Resistor Calculator gives Resistance Ohms: 350, Power Mw: 140.

よくある質問

Where do I find my LED's forward voltage and current?

Check the LED's datasheet — common values are around 2V forward voltage and 20mA current for standard indicator LEDs.

What happens if the resistor value is too low?

Too little resistance lets excess current through, which can burn out the LED.

What inputs does the LED Resistor Calculator need?

You'll need to provide: Supply voltage (V), LED forward voltage (V), LED current (mA). All fields use sensible defaults, so you can see a working example immediately and then adjust the values to match your own numbers.

How accurate is the LED Resistor Calculator?

The LED Resistor Calculator applies the formula exactly as calculated — Resistance = (supply voltage − LED forward voltage) / LED current. Power = (supply − forward voltage) × current. — so results are precise for the inputs you provide. Accuracy depends on entering correct, realistic input values.

Is the LED Resistor Calculator free to use?

Yes, the LED Resistor Calculator is completely free, requires no signup, and runs instantly in your browser.