LED-Vorwiderstands-Rechner

Berechnen Sie den exakten Vorwiderstand-Wert und die Leistung für Ihre LED-Schaltung. Geben Sie Versorgungsspannung, LED-Vorwärtsspannung, Strom und LED-Anzahl ein, um den Widerstandswert, die Leistungsaufnahme und den nächsten Standard-E12-Widerstand sofort zu erhalten.

Supply Voltage
V
LED Forward Voltage
V
LED Current
mA
LEDs in Series

How to Calculate LED Resistors

Ohm's Law

Ohm's Law: R = (V_supply − V_led) ÷ I_led

Formula

Formula: R = (V_supply − (V_led × N)) ÷ I_led

LEDs require a current-limiting resistor to prevent damage. The resistor drops the excess voltage from the power supply while limiting current to the desired value. Always use a resistor with a higher power rating than calculated.

Common LED Forward Voltages

Resistor Power Rating

Use a resistor with at least 2× the calculated power dissipation for safety. Common ratings: ¼W (0.25W), ½W (0.5W), 1W, 2W.

Über LED-Vorwiderstands-Rechner

This free online calculator helps you find the ideal current-limiting resistor for any LED circuit. Whether you are building an Arduino project, repairing electronics, or designing custom lighting, choosing the correct resistor is essential to protect your LEDs from excessive current and ensure long lifespan. Simply enter your supply voltage, LED forward voltage, desired current, and number of LEDs in series to get the resistor value, nearest standard resistor, power dissipation, and color code. All calculations happen entirely in your browser — no data is sent to any server.

Features

How to Use the LED Resistor Calculator

  1. Enter your power supply voltage (e.g., 5V for USB, 12V for automotive).
  2. Enter the LED forward voltage (Vf) or use a preset button for common colors (Red 2.0V, Green 2.2V, Blue 3.2V, etc.).
  3. Enter the desired LED current (typically 10–20 mA) or use a preset.
  4. Specify how many LEDs are connected in series (default is 1).
  5. Click Calculate to get the resistor value, standard resistor, and color code.
  6. Use the Copy button to save the results to your clipboard for your project documentation.

Common Use Cases

Frequently Asked Questions

Was ist die LED-Vorwärtsspannung?

Die Vorwärtsspannung (Vf) ist die Mindestspannung, die eine LED benötigt, um zu leiten und Licht zu emittieren. Typische Werte: Rot (1,8-2,2V), Grün (2,0-2,4V), Blau/Weiß (3,0-3,3V), Gelb (2,0-2,2V).

Wie viel Strom sollte ich verwenden?

Standard-LEDs arbeiten typischerweise bei 10-20mA für volle Helligkeit. Höhere Ströme erhöhen die Helligkeit, reduzieren aber die Lebensdauer und erzeugen mehr Wärme. Prüfen Sie immer das Datenblatt Ihrer LED für die maximale Belastung.

Was ist die E12-Widerstands-Serie?

E12 ist eine Standard-Widerstands-Serie mit 12 Werten pro Dekade (1,0; 1,2; 1,5; 1,8; 2,2; 2,7; 3,3; 3,9; 4,7; 5,6; 6,8; 8,2). Diese sind allgemein verfügbar und für die meisten LED-Anwendungen ausreichend.

Kann ich mehrere LEDs in Reihe schalten?

Ja, Sie können LEDs in Reihe schalten. Der gesamte Spannungsabfall über alle LEDs muss kleiner sein als Ihre Versorgungsspannung. Die restliche Spannung fällt am Widerstand ab.

Was passiert, wenn ich den falschen Widerstand verwende?

Zu niedriger Widerstand → zu hoher Strom → LED brennt schnell durch. Zu hoher Widerstand → zu geringer Strom → LED ist dunkel oder leuchtet nicht.

Can I connect multiple LEDs in series?

Yes, you can connect multiple LEDs in series. The total voltage drop across all LEDs must be less than the supply voltage. The resistor drops the remaining voltage. The calculator validates this automatically and warns you if the supply voltage is insufficient.

What happens if I use the wrong resistor value?

A resistor that is too small allows excessive current, causing the LED to be very bright but shortening its lifespan or burning it out. A resistor that is too large limits current too much, making the LED dim or not light up at all. Always use the calculated value or the nearest standard resistor.

What is the resistor color code?

The resistor color code uses colored bands to indicate the resistance value and tolerance. For example, brown-black-brown = 100Ω ±1%. The calculator shows the color code for the nearest standard resistor, making it easy to find the right component in your parts bin.

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