LED Resistance calculator

LED Resistance

Resistor ValueXXXX Ω
Wattage RecommendationXXXX W


Supply Voltage:


Forward Voltage:


Forward Current:


Number of LEDs:

Decimal Place

The LED is a semiconductor and therefore requires the use of a resistor in series with it so that they do not burn out. The LED Resistor calculator will calculate the correct value of LED resistance by using Ohm’s Law to solve for R, which is then used to calculate LED voltage drop or current (using Ohm’s law equations). LED Resistors have different value ranges, and the LED Resistance calculator will calculate LED resistor values for each range.

Below is more information on how to use the LED resistor calculator:

The LED resistor values can be entered in standard ohm notation as R, 1R, or 100R (for red, orange, or yellow LEDs). The LED resistor values can also be entered as LED voltage drop (V or VDC), LED forward current (mA), or LED Power in Watts.

A green LED typically has a forward voltage drop of 3.1 volts and requires less than 20 mA of current to operate. A common red LED has a typical forward voltage drop of 2.0 volts and a forward current in the range of 20-30 mA.

The LED resistor calculator will also determine LED Power (in Watts) based on LED forward voltage drop and LED Forward Current.

Using Ohm’s Law equations, LED voltage drop = R * I, V=IR or P=IV

LED resistor value to ensure there is no LED LED voltage drop when LED is activated (on)

(Ohms Law V=IR or P=IV) LED resistor value to ensure LED does not burn out when LED is on for a long time.

Calculate LED Resistor LED voltage drop R, LED resistor value for 3.1V 2mA Green LED Calculate LED resistance to have NO LED LED voltage drop when GREEN LED is activated (on) Calculate LED resistor value if you want to ensure the LED does NOT burn out when GREEN LED is on for a long time

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