Calculate the series resistor LED. (And the E12 color code.)

LED series resistor schematic. Calculate the series resistor for a LED. Copyright © Bruno Stroobandt infonosity.net

LED series resistor calculator: Here you can easily calculate the series resistor for a LED. Also for more LED’s in series. And this LED calculator automatically searches for the correct resistor in the E12 series. NEW: The LED ballast series resistor calculator now also gives the E12 resistor colorcode (color bands code) 😎 Later in the article also: How to calculate the series resistor for a LED by hand.

Calculate the series resistance LED.  Looks for proper resistance in the E-12 series.

The voltages in the picture are for standard LED’s. Special LED’s can differ, but that is also stated on the packaging.

More info about what is an LED (Dutch , English via Google translate in the top left corner)

P.S .: I am talking about an LED calculator here, but you can use this just as well if you want to, for example, have a 6-volt bicycle light lit with the 12-volt power supply of your model train power supply or a car battery, for example.

Calculate the series ballast resistor LED. And color code.









Fill in the fields above

and click on calculate

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here comes the color code


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Series resistor power: (take at least the first higher value of the calculation above) Resistor consists of 1/8 = 0.12 Watt, 1/4 = 0.25Watt, 1/2 = 0.5Watt. And higher but that does not apply here. 🙂

☠️If the power is too low, there is not only a risk of failure of the resistor. But it can get so hot that you run the risk of burning yourself or even burning a fire !!!☠️

Calculate series resistor. LED long pin = positive. LED short pin = negative.

Long leg LED = positive, LED short leg = negative.

How to calculate the series resistance for a LED? For Your Information – formula’s.

How can you make the calculation for the LED series resistor yourself?

  1. Take the LED voltage x number of LEDs in series. (Uleds)
  2. Then take the (battery voltage) – (the total LED voltage). = Ubat-Uleds.
  3. This is the voltage that the ballast series resistor has to get rid of. (VR)
  4. Then you divide VR by the LED maximum current = R (=minimum resistor you need)
  5. And then in the E12 series you search for the first higher resistance.
  6. BUT !!! You also need to know how many watts of power this R should be.
  7. For that you do VR x LED maximum current. = P (power, power)

Series resistor LED E12 series.

What are e12 resistors? The E-12 series is sufficient to use as a series resistor for an LED. These have a tolerance of +/- 10%, therefore no intermediate values ​​exist. (They do exist, if this is important. For example in the E24 series, but they are more expensive !!!!)

E12 resistor, means that the values ​​between 1 and 10 are divided into 12 steps. There are also multiples of 10 of these.

E12 series resistor. are:

  • 1.0 ohm.
  • 1.2 ohms.
  • 1.5 ohms.
  • 1.8 ohms.
  • 2.2 ohms.
  • 2.7 ohms.
  • 3.3 ohms.
  • 3.9 ohms.
  • 4.7 ohms.
  • 5.6 ohms.
  • 6.8 ohms.
  • 8.2 ohms.

And after 8.2 ohms comes 10 ohms, but that is a tenfold back 1ohm.

Calculate series resistor color code E12 series.

On the E12 series of resistors you see 3 colored stripes close together. And then a little further a fourth line. You have to hold the resistor in front of you so that the 3 stripes are together to your left. And then you can read the value.

The first 2 are just numbers, the third is a power of 10

There is a trick to memorize the order of colors. “Black Beetles Running Over Your Garden Bring Very Grey Weather”

  • Black = 0
  • Brown = 1
  • Red = 2
  • Orange = 3
  • Yellow = 4
  • Green = 5
  • Blue = 6
  • Violet = 7
  • Gray = 8
  • White = 9
LED ballast series resistor. 1000 ohm = brown - black - red

Example. Brown-Black-Red = “1”, “0 ″ and that x “ 10 to the second power” => 10 × 100 = 1000 ohms or 1k (ilo) ohms = or short: 1k.

Example 2. Yellow-Violet-Orange = “4”, ”7 ″ x 10³ => 47 × 1000 = 47k.

If the third ring = gold. Then its just the first 2 numbers / 10. (yellow-violet-gold = 1.2 ohm)

If the third ring is silver. Then its the first 2 numbers / 100. (yellow-violet-silver = 0.12 ohm)


P.S.: The fourth ring gives the tolerance. (accuracy) Silver = 10% and Gold = 5%. And there are even more precise resistances. But a) they are more expensive, and b) this is necessary, for example, to make a radio transmitter, but not as a simple series resistor.

(At E24 and better you have a dash more as a number. So 3 numbers, the fourth is the power and at the back (right) you also have red = 2% tolerance and brown = 1% tolerance)


DIY electronics – fun

How to turn 1 LED on and the second LED off with one electronic switch? 2 LED control display. (Can be used for model-train projects)


External: google electronics parts stores

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