LED电阻计算器

计算LED电路的精确串联电阻值和功率额定值。输入电源电压、LED正向电压、电流和LED数量，即可获得电阻值、功率耗散和最近的标准E12电阻值。

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.

关于LED电阻计算器

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

什么是LED正向电压？

正向电压(Vf)是LED导通并发光所需的最小电压。典型值：红色(1.8-2.2V)、绿色(2.0-2.4V)、蓝色/白色(3.0-3.3V)、黄色(2.0-2.2V)。

应该使用多大电流？

标准LED通常在10-20mA下达到全亮度。较高电流增加亮度但缩短寿命并产生更多热量。请务必查阅LED数据手册了解最大额定值。

什么是E12电阻系列？

E12是标准电阻系列，每个数量级有12个值(1.0, 1.2, 1.5, 1.8, 2.2, 2.7, 3.3, 3.9, 4.7, 5.6, 6.8, 8.2)。这些电阻常见且足以满足大多数LED应用。

可以串联多个LED吗？

可以串联LED。所有LED的总电压降必须小于电源电压。剩余电压由电阻分担。

使用错误的电阻会怎样？

电阻过小 → 电流过大 → LED快速烧毁。电阻过大 → 电流不足 → LED昏暗或不亮。

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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