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LED Resistor Calculator

You will find this LED resistance calculator very useful for calculating the exact value, power, dissipation of a resistor for the selected LED. This tool will also allow you to calculate the resistor for many LEDs in series by assessing its total forward voltage drop value. The software will also enable you to calculate resistors for different colored LEDs such as red, white, blue green having different forward voltage drops.

Inputs

(Vs)

(Vf)
If (mA)
 
 

Outputs

(Ω)
(W)
(W)

11 thoughts on “LED Resistor Calculator”

  1. Hi Mr Swag, thanks for helping. I ask your advice on resisters for 12 volt LED lights. You suggest 6omh x 1watt resistor. I can only obtain 5.6 or 6.8 x 1 watt resister. witch one must I use

    Regards
    Gerhard van Aswegen

    • Hi Gerhard, in general electronic circuits nothing is too critical, so you can use any one of those resistors…6.8 ohm will be safer, so you can go for that!

  2. Hi Mr Swag. 250 watt panel, 30 amp charge control, 12 volt 150 Ah d/c battery. Lights connect direct to battery. use one common + and – line but separate wires and switches to switch lights on and off

    • Hi Gerhard, for a 12 V 350mA LED, the current limiting resistor can be calculated as shown below:

      R = (14 – 12) / 0.35 = 5.71 ohms or 6 ohms
      watts = 0.35 x 2 = 0.7 watts or 1 watt

      So you can connect 6 ohm, 1 watt resistor in series with each 12 V 350 mA LEDa, but make sure the input supply to the bulbs are never more than 14.5V

  3. Hi Mr Swag, Please help. I am using 3 watt LED ceiling lights without a driver on solar, but it keep on blowing the one led in the light. If I use more than one light on the circuit it do not blown the led in the lights. I remove the driver to use on 12 volt circuit. Power input on driver AC85 – 265 VOLTS 50 /60hHz
    Output DC 3-12volts 300mA+5%.I want to use on separate circuit. Do I need to put a resistor in circuit and what size do I need.
    Please help

    • Hi Gerhard, can you please provide the solar panel voltage specs, then I can suggest how to calculate the resistor.

  4. Hi Mr swag.pls I need a Need a simple 12v 5min timer with relay circuit that has reset button.A button to trigger timer to off relay after 5minute and another reset button to on the relay back,but even though the power supply is removed and refixed it should not have effect to reset it.

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