Size a Current-Limiting Resistor for an LED

Work out the resistor value an LED needs from supply voltage and current.

Tiada log masuk diperlukan

Voltage (V)

Current (I)

Resistance (R)

Power (P)

Enter any two values and the other two are solved automatically

💡 Ohm's law: V = I × R. Power adds P = V × I. Knowing any two lets you derive the rest — handy for sizing resistors, checking LED current, or working out heat dissipation.

LEDs tips

💡

Resistor value R = (supply V − LED forward V) ÷ LED current. Enter the voltage drop and target current to get R.

🎯

A typical LED wants ~20mA (0.02A). With a 5V supply and a 2V LED, that needs ~150Ω.

⚡

Check the power too — the calculator shows watts so you can pick a resistor that won't overheat.

Cara ia berfungsi

Masukkan

Enter your data into the tool above. Everything stays local to your browser.

Proses

The tool processes your data instantly in your browser using JavaScript. No server, no waiting.

Muat turun

Get your result instantly. Nothing is stored after you leave the page — complete privacy.

Mengapa alat kami?

✓Percuma sepenuhnya — tiada kos tersembunyi, selama-lamanya

✓Tiada akaun, e-mel atau log masuk diperlukan

✓Fail tidak pernah meninggalkan peranti anda

✓Tiada had saiz fail langsung

✓Tiada tera air pada sebarang output

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