LibraTool logoLibraTool
⚡
💡

Size a Current-Limiting Resistor for an LED

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

Níl gá le logáil isteach
V
A
Ω
W
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.

Conas a Oibríonn sé

1
Cuir isteach
Enter your data into the tool above. Everything stays local to your browser.
2
Próiseas
The tool processes your data instantly in your browser using JavaScript. No server, no waiting.
3
Íosluchtaigh
Get your result instantly. Nothing is stored after you leave the page — complete privacy.

Cén fáth ár gceann a úsáid?

✓Go hiomlán saor in aisce - gan aon chostais i bhfolach, riamh
✓Níl cuntas, ríomhphost ná logáil isteach ag teastáil
✓Ní fhágann comhaid do ghléas riamh
✓Níl aon teorainn le méid comhaid ar bith
✓Gan comhartha uisce ar aon aschur

Also check out…

🔥

Calculate Power Dissipation (Watts)

Find how many watts a component dissipates so you

🎓

Solve Ohm's Law Homework

Check circuit problems by entering any two known v

🔋

Estimate Current Draw from a Battery

Find the current a load pulls so you can estimate

📉

Calculate Voltage Across a Component

Find the voltage drop across a resistor from curre

Ceisteanna Coitianta

Back to Ohm's Law Calculator