LED Resistor Calculation

How do you select the right size resistor for an LED? This video will guide you through the calculation to select the proper current-limiting resistor for an LED, given the LED's forward voltage drop, desired current, and the voltage of your power supply. It also covers more complicated scenarios like combining multiple LEDs of different colors in series or parallel, and how to make sure you don't exceed the power rating of your resistors.
Don't have the right resistor value laying around? Check out this video to learn how you can combine resistors in series and parallel to create almost any value you need: • Resistors in Series an...
Don't understand why I said it's OK to put the LED before the resistor? Watch this video for an explanation: • Does the resistor need...
Have a question? Ask in the comments and I'll do my best to get back to you.

[@MrRofl131]

Finally found someone who knows his stuff and explain it in a very clear way. Thank you!

[@BenFinio]

Thanks!

[@juharautiainen8931]

It was very good to understand that when putting LEDs in series, you don't multiply currents each LED requires.

[@UstedTubo187]

This is the first video (of MANY) that I've come across that actually shows how to find the voltage and current for an LED, or actually uses the terms one sees in the data sheets for that matter (forward voltage and forward current). All other videos explaining how to calculate the resistor just say, "...and this LED has a voltage drop of 2V." Thank you for explaining in a practical, applicable way!

[@deleted3792]

Excellent teacher, i love the practical knowledge I used to do this in my GCSEs but never got the application part but you've shown exactly where it would be applied to real life. You are a W guy!

[@theintelarif]

Thanks for explicating each of the cases comprehensively, sir. The succinctness of your tutorials is truly appreciable.

[@RetroHoo]

I had electronics in school roughty 25 years ago, so I was a little rusty... I've seen more than a couple of videos to refresh, but this one is by far the best. Thanks!

[@mytzusky]

what a gold mine this video is, thank you.

[@assamesestatusview]

Most easy and best way to learn

[@jeanpierreragequit1726]

A very clear explanation for my modelism lights. Thank u so much.

[@jimthigpen333]

I've watched so many video's on LED lighting today that you might as well have been speaking Chinese . Brain overloaded . A great video for sue but I need it in slow motion . You talk faster that I can think ! I need a nap !

[@BenFinio]

If you have a specific question about part of the video, feel free to leave a comment and I'll do my best to answer it.

[@kabandajamir9844]

The world's best teacher thanks sir

[@anthonychampagne6239]

Thank you for this informative video No joke dude I actually thought you would have thousands of subscribers u deserve it

[@BenFinio]

Well, it took a year, but now I have more than a thousand subscribers!

[@KennethSorling]

This was a great tutorial, but still way over my head. At 55 years of age, I feel I need to go back to school and re-learn the basics of electronics. I feel a real temptation to do so, though, so that's a good reflection on your video.

[@BenFinio]

No need to go back to school when it's all on KZbin! Check out my intro to circuits playlist, you may find this helpful: kzbin.info/aero/PLKL6KBeCnI3U6KNZEiitdtqvrxkBhpuOp

[@dfuzesavetf2147]

how can you only have 187 subs with such high quality vids

[@BenFinio]

Haha, thank you - most of these tutorial videos are relatively new and I don't post them that often, so that probably explains it.

[@virtuallyhappy1888]

Bro has 9k subs now.. And that's what I called the result of dedication

[@DreagNohud]

Up to 11.9 now

[@garymucher4082]

I realize this is an older video. But no need to look up anything or to find the forward voltage drop to any LED. Merely take the supply voltage and divide by ~20ma or less and WALA, you have the resistor value. No need to look up anything, and too many times you have no idea what type LED you have. So merely pick your resistor for 20ma or less and it will work every time... JMHO!

[@carolscott6644]

clear and concise, very illuminating!.....Al Scott

[@ChryslerLeBaro]

Dude! Thank you, this was super helpful. I’ve always struggled with this math, and this broke it down a way I could really digest.

[@AdaManfaat]

you nailed it. nice presentation, nice knowledge, nice appearance. you deserve more views

[@freebeardgaming]

Thanks for this, very good examples for someone who is just learning about using leds and a breadboard!

[@SebVEVO]

Nicely explained. The only thing I did not understand is how the breadboard parrallel connection with your multimeter plugged in at 6:42 works.

[@larrybud]

Very nice video. In respect to LEDs themselves, read your datasheet and it should have relative luminosity at a specific current. That way if you're doing RGB stuff, you can figure out what current you want in order to make the relative brightness between each color the same.

[@VideoProducer]

Thank you! Answered my question and explained it well. Been too many years since my junior high electronics class I have forgotten everything.

[@christopherhydes8985]

Thanks for your help. This is video gives a clear and concise explanation. well done!

[@BenFinio]

Thank you!

[@AlejandroPerez-vf7jv]

Dr. Ben Finio, thank you for the video, you made things easy to understand. I will subscribe and watch more of your videos, they are awesome!

[@BenFinio]

Thank you!

[@SeeKay55]

Nicely explained an demonstrated, doc. You’ve got me as a subscriber.

[@BenFinio]

Thanks!

[@PrayagSanjay]

Most compehrnsive video on resistor value. Thanks.

[@VSN95]

Nailed it. Thanks for going through every scenario

[@LawalAbdurrahmanOlatunde]

Wow this was so helpful, thanks. The explanation was so clear without knots.

[@Sven2157]

Not sure why, but my dyslexia doesn't affect me while learning this from you. Thanks!

[@orveahava]

Thank you for your work. Finally i get it.❤👍

[@IoSonoPiero]

You deserve a lot of subscribers. Great educative video!

[@dardale9050]

It’s the conventional flow thing, and then calling it current. Call electrons like it is or confuse the watchers who probably understand electron flow theory. Good picture quality and explanation with rated resistors! Thanks for sharing.

[@BenFinio]

Relevant XKCD... xkcd.com/567/

[@Coolgiy67]

We stick to conventional flow cause we can use right hand rule to find the magnetic fields 😁

[@Hidegety1]

Very well put together

[@arpitjain4025]

very well and clearly explained with practical. keep it up. love from INDIA

[@BenFinio]

Thanks, glad it was helpful!

[@JusticeAlways]

Good presentation! I'm little lost on resistor power handling...heat dissipation. Like when to use a 1/4 watt instead of a 1/8 watt (example). I had a project to use LED lights on a golf cart. Cart batteries were 8.43 vdc each. I had LEDs using 4.5 vdc. Not knowing current draw of LED....I started off with 100 ohm resistor...had 2.7 vdc to LED...was very dim illumination. Then tried 33 ohm (was 1/4 watt)...got 3.2 vdc to LED...was little brighter...then tried a 10 ohm (was a 10 watt)...got 3.9 vdc to LED....was much brighter. By seeing my results I figured to get the 4.5 vdc I would need a ~ 2 ohm resistor (to achieve optimal light illumination of LED...rated as 100 lumens output). I noticed I could not read actual drop down voltage out of my "circuit" until there was the LED load put on it. Had fun playing with it....not an "orthodox" way of designing...didn't have the current draw specs of the LED. Not sure if this is an acceptable way to do it. 😁 Just curious if my estimation of the 2 ohm resistor is correct. And would a 5 watt rating work?

[@shsftech3792]

Wowwww this is very to understand all my question are already answered upon watching this thank you Dr.!

[@BenFinio]

You're welcome!

[@rodpearson3967]

tbh, i was very pleased with the presentation its informative and well, easily understood. i wish they did this when i was in grade school. couldve made things so much different for my life today.

[@phillcasedy2228]

Thank you verry clear explanation.

[@rhm504]

So awesome! Thank you for explaining this so clearly.

[@mikefromflorida8357]

Good information and approach to the topic. This is KZbin and not a classroom, so referring to yourself as doctor neither needed nor desired.

[@SVSunnyJim]

I so needed this tutorial. Spot on buddy.. 👍

[@markpereira3931]

your video is going in my playlist . well explained !

[@komatsu575]

Absolutely awesome education video explaining about the LED's!! Thanks so much!!!

[@linkmasters535]

Thank you so much for this information on the green led with a 100 ohm resistor would it make the led last longer instead of to much power to burn the led out

[@JohnSmith-ix6ts]

Excellent video, thank you.

[@ramudumyla2569]

thanx for nice explanation

[@nicolemitchell446]

This is exactly what I needed to know. Thank you

[@RixtronixLAB]

Nice video shot, thanks for sharing it with us, well done :)

[@blasttrash]

wow amazing. you need more susbcribers. amazing explanations.

[@BenFinio]

Thank you! It's been quite a while since I've made a video and I usually make them to go along with something on Instructables www.instructables.com/member/Ben%20Finio/instructables/

[@elegeblege1618]

Thanks a lot for great explanation. However, one huge minus is using that marker - when you write on paper with it I got goosebumps (I hate that sound irl)

[@real_model_construction757]

Hi Ben! First off, thank you so much for posting these highly useful videos! ....one of my next projects will be scratch building a scale model of about a 13-story tall office building, and lighting up each floor individually. I will be using between 5-10 clear white leds on each floor, and some colored leds for exterior lighting. Im thinking about wiring the entire building in parallel, and combining every two floors into individual parallel circuits, using 2 AA batteries for each one....do you think this would work? Any suggestions?

[@danwinter8395]

Hello, very nice video. If you were able to supply an LED the exact same voltage that it requires, would your calculations come out to zero ohms, or no resistor needed? For all of your examples, the voltage provided was above the voltage required, so I understand needing a resistor in those scenarios. Thank you.

[@EonTide1111]

Why is the one led vd 3.2v at time stamp 10:30?

[@linearz]

The best explanation! Very good presentation.

[@malualf]

Thank you, this was so usefull and clear, please make many many more. Greatings from Argentina.

[@BenFinio]

Thanks! If you check out the playlists on my channel you will see many other electronics and Arduino tutorials that I hope you will find useful.

[@malualf]

@@BenFinio I have seen and I would love to see many more!!!

[@gugabernardo]

Phenomenal explanation, thank you!

[@GB-rb1up]

Thank you. Clear explanation.

[@angel_machariel]

That was as clear as it gets. Thanks!

[@hassanmunir]

Thank you for this explanation.

[@ericklassen742]

Hey, Thanks for not replying. I was thinking of subscribing but you solved that question for me.

[@BenFinio]

KZbin stopped sending me comment notifications for some reason and I am working through a giant backlog of comments on this channel.

[@kevintanudjaja7597]

Thanks

[@hafizzulqarnain5379]

Which LED colour uses least current?

[@956miggz]

Can connect a 3v led with a resistor and a 12v led to the same 12v battery? Does the resistor limit the 12v as well?

[@lilsix9218]

What resistor could i use if i put together the red and green led on 9v battery?

[@Faizy_Ahmad]

Brilliant explanation

[@mhnoni]

Hi, thanks for the great explanation, I have a question for calculating the value of the resistance @ min 10:46 , why did you put 0.02 for the current when we have 2 LED? Isn't that supposed to be 0.04? or that's because we connected the LED in parallel?

[@newfie-dean5803]

I have a car license plate bulb socket that requires a resistor to make an LED bulb work in the socket. If I use an axial resistor and connect one wire end to the left socket contact and the other wire end to the right socket contact and then insert the bulb into the socket is that a series connection? Also, if I calculate a 115 ohm, 1W resistor could I go with a higher power rated resistor like a 5W? I believe I read you can do that. In this case if you chose a 100 ohm resistor would that be close enough or should you be at or above the calculated resistance value? Thanks for your time!

[@thinkbeyond5360]

I have a question 5mm fat led datasheet is missing... How do I find out

[@tomjpt]

Or to put my question a different way: What is the difference between voltage drop and forward voltage?

[@billcianci7945]

Excellent! You make it very easy to follow... thank you!

[@andreasaa2563]

This is amazing

[@--_-_-_-_-_-_-_-_]

I am using 330 ohm resistors but my leds are still too bright, I piwer the leds directly from an esp32

[@kennmossman8701]

NOT recommended

[@epiendless1128]

Yup. I find modern LEDs, (and I mostly use surface mount ones) are way too bright if you run them at their datasheet current. Looking at a Firebeetle ESP board, their LED resistor is 2.4k for less than a milliamp. I know the LED calculation like the back of my hand, but these days I just bung in a big resistor and see if it looks OK.

[@pradeepmahendrasemage4043]

Nice, Thanks.

[@billhandymanbill2775]

Nice video! The only thing I would have liked to know more about is the construction of the LED and which side to attach the resistor and which side of the LED to attach to + or - of the battery.

[@BenFinio]

Honestly I always get "cathode" and "anode" mixed up and find it easier just to remember that the long lead is the positive one. This diagram is a good one though: qph.fs.quoracdn.net/main-qimg-54791c1af8a06f2051c64b9d0c4d7f55

[@PetrikNZ]

@@BenFinio Think of it in terms of exam results. (C)athode, (A)node. Scoring a C in the exam would be a negative result, scoring an A a positive result.

[@BenFinio]

@@PetrikNZ Never heard that one before - helpful, thanks!

[@_russl8]

Very helpful video thanks it helped me understand my tech hw

[@BenFinio]

Glad you found it helpful!

[@arduinomaquinas]

Very cool 🇧🇷😉👏👏👏👏👏 awesome video !

[@gamingaddict2944]

Im just starting teaching myself. Your the man..

[@AditPatidar]

Hi, What are the green wires on the circuit board between the LED's and the plus voltage?

[@general-e8628]

I try drop my reciver voltage from 6 volts to 5.5 volts. I thought it would be 1 or 2 ohm resistor but it took 1M resistor to do it. I am bit confuse why that is 🤔

[@elixpo]

Ben Eater and and Bean Finio damn ❤️❤️

[@justcomments9326]

Need help. I want a simple led and resistor and diode combination which will glow the led at exact 4.2V. My BMS does not have led indicator to show li-ion battery is fully charged.

[@karhukivi]

Google on "Li-ion battery indicator light circuit" and you will get several circuits. To get a precise voltage point for turn-on, a zener diode or else a voltage-divider of two or more resistors will be needed.

[@brandonhagerty6089]

At 1:14 it's said that using extra batteries will waste power because it will be burned off by the resistor, but at 4:39 it's said that if you reduce the current from having a stronger resistor you can extend your battery life. These two statements seem like they're in opposition. Could someone please elaborate?

[@kennmossman8701]

you are wondering about apples and oranges - two very different things

[@normanbeaulieu4204]

Yeah I have a question. I have a power supply (coin cell) of 3.7V I need to power 3 LED Filaments that are 3V at 50 - 100 milliamps. Do I need to add more power to run them? How money resistors would I need? And What resistor would I use? I don’t want to overheat anything? Just FYI I have a 6V power supply if I need it.

[@BenFinio]

A coin cell battery may not have enough current to power that many LEDs. You can typically power a single LED with a coin cell battery without needing a resistor, because the current they provide is so small. This video may help, as well as the introduction to circuits playlist on my channel: kzbin.info/www/bejne/kJWsc5-blJ6MlZY

[@johnlloydcalisi3257]

thank you!

[@BenFinio]

You're welcome!

[@xhuljan11]

Thanks,You Are King 👑

[@acurbow]

So if I want to run 8 3v multi colored flickering leds off a 12 volt power supply what size resistor would I use

[@BenFinio]

You watch the video and learn to do the calculation yourself :-)

[@johnellis8271]

Hi Ben I have 90 LED 2v all individually switched obviously will each have their own resistor what is the lowest and highest power I can run these on and what calculation would I use pleas kind regards John

[@johnellis8271]

Sorry I should have said run in parallel

[@joter-glem]

It explane more but I still cann't put all together. What is current of the battery? Why is it not importent? What will be the difference if I use 5V 0.5A or 5V 0.9A (USB supplied power)

[@BenFinio]

Hi - you may find my intro to circuits playlist helpful: kzbin.info/aero/PLKL6KBeCnI3U6KNZEiitdtqvrxkBhpuOp. For the supplies you mentioned, 500mA (0.5mA) is already more than enough if you are only lighting up a few LEDs - if each LED only needs 20mA that's enough for 500/20 = 25 LEDs.

[@RKELLEHER40]

Howdy, Brother! What resistor should I use if I have a yellow 10mm LED Emitting Diode (1.8-2.2V) powered by two AA Batteries (on/off switch in the loop)? I'm not even sure if I asked the question properly 🤠. Thanks for any assistance.

[@RKELLEHER40]

45 ohms?

[@beelzzebub]

What if I have a 3v battery and 10 3v LEDs, all in parallel - do I even even need a resistor? Should I assume my resistor might draw a small voltage of say 0.1V and then use 200mA as my current? (10 LEDs at 20mA to get 200mA). Under that assumption that my resistor draws 0.1V, my resistor would be 0.5 ohms, maybe even less... (and my Imax for a 1/4watt resistor would be 700mA, so way above the 200mA draw).

[@BenFinio]

If it is a coin cell battery then you can probably use it without a resistor. I don't have time to help you with the math but these two videos may help your conceptual understanding: kzbin.info/www/bejne/kJWsc5-blJ6MlZY kzbin.info/www/bejne/l2nHY2WPhpeke9k

[@beelzzebub]

@@BenFinio It’s actually likely to be a dc power supply - does that change things?

[@BenFinio]

@@beelzzebub yes, the DC power supply has a much lower internal resistance and would be more likely to burn out the LEDs so I would use a resistor just to be safe.

[@beelzzebub]

@@BenFinio But how can i calculator the resistance needed if the voltage supply (3V) is equal to the LED’s forward voltage - R = V/I will always give 0, implying no resistor needed right? Or maybe you’re just recommending any low ohm resistor?

[@BenFinio]

@@beelzzebub assume a slightly lower operating point for the LED, e.g. 2.9V

[@albertanasoul]

Great video, thank you for making it. How do you figure this out when you don’t know the values of the LEDs you are using?

[@BenFinio]

Hi Michael - the voltages for LEDs are pretty standard based on the color. Just google "LED voltage color chart" and you will find a bunch of them. Almost all of the "regular size" LEDs (the kind you see in this video) are rated at 20mA, so that is usually a good guess to start. To be safe, you can always start with a bigger resistor, measure the current through the LED (assuming you have a multimeter - separate tutorial on that coming soon), and then move down to a smaller resistor if the current is still below 20mA.

[@abdoustube]

Thank you for the video. What can one do if they don't have info about the voltage drop and current of the led

[@BenFinio]

The voltages for different colors are pretty standard, usually starting around 2V for red up to around 4V for blue or white. So to be safe, you can assume a higher voltage and target a lower current (10mA), and start off with a large resistor (say 1kohm). Take measurements and work your way down to a smaller resistor. If you are using standard 5mm LEDs then from what I've seen the current is almost always 20mA.

[@abdoustube]

@@BenFinio Thank you very much

[@ericklassen742]

Great video! I have an LED string with non-removable bulbs and 1/2 of the string is dead. I have found the bad bulb and I want to cut it out of the circuit. I know that I have to replace the bulb with a resistor but, since I have no data on the string of lights, I don't know what value of resistor to use to phase out the dead LED. Suggestions?

[@kennmossman8701]

not even info is given. if you like try a 330 Ohm resistor ...if too dim, try 220, if too dim try 100, etc

[@BenFinio]

In general if you are in a guess-and-check situation with resistors, it's safer to start with a very high value and work your way down. If you start low you are more likely to burn something out by having too much current.

[@criticalthinker7822]

I have a 12V LED and a 24V power supply. Would a resistor protect my LED?

[@BenFinio]

If you are referring to a 12V LED strip, those are typically designed to work with a 12V power supply. They consist of sets of 3 LEDs in series and include current limiting resistors in the strip. In theory you could use a single external resistor with a 24V supply but it would be dissipating a LOT of power so you'd need to make sure the resistor could handle the power. It's probably better to just buy an appropriate 12V supply.

[@eganwill]

what if i need 15 LED? what battery and resistor should I use?

[@BenFinio]

Sorry, you'll have to watch the video and figure that out yourself :-)

[@jimcatanzaro7808]

Could you add a small capacitor between each diode for voltage stabilization

[@martinkuliza]

Try it LOL in an AC Circuit a Cap will smooth out the voltage spikes or ripple that you have because the difference in charge from one plate to the other will allow current to flow through teh capacitor HOWEVER..... in DC Circuits With the capacitor empty With the capacitor connected to the power supply , Let's assume you have a 5V Supply and a 10V Capacitor well.... Your capacitor will charge up to the voltage of the supply and no further but since it's not AC but DC Current won't flow through it and your LED will turn off if you wanted to control the voltage you could always put a voltage regulator on the line before the LED, it'd serve the same purpose

[@ClickClack_Bam]

I'm a total noob at this. Can you use a capacitor to store energy from the battery so it's not wasted? So can you apply a capacitor that will take in the energy from the battery & apply what's needed to the LEDs so that your circuit becomes more efficient & less wasteful?

[@BenFinio]

I can't really answer this question in a short youtube comment - I don't have my own videos about capacitors, but there will be plenty of other videos out there about them.

[@karhukivi]

The short answer is no. A capacitor stores energy as electric charge but the voltage across it can vary by a large amount and potentially destroy the LED. A battery stores chemical energy but the terminal voltage only varies by a relatively small amount, so more suitable for powering electrical and electronic devices.

[@zaksept]

This is a really good video, thanks for making it and posting it. It will be helpful for my project. My only criticism is that it would be more helpful if you included the units (mA, A, V, etc.) next to the numbers to help understand the formulas and calculations. Will be subscribing to this channel as its so helpful.

[@BenFinio]

This is a good example of "do as I say, not as I do" - you're right, it's always a good idea to write out units in the equation for clarity, not just in the final answer. Sometimes I get lazy about it!

[@doncodman913]

Hi Ben . Lovely video explaining the maths and the valuable point about not making an error of adding up the forward ampage in a LED in series circuit. I have a question ,please. On resistors size my little project works out the power going thru my resistor is 0.029w , does it make any difference if i was to use a 0.125w power rated resistor , to say , using a 0.500w power rated resistor ? Hope you could help. Look forward to hearing from you . Regards Don Codman

[@IthacaNature]

Hi Don - as long as they have the same resistance, it doesn't change the math for the current going through the LED. Resistors with bigger power ratings will generally be more expensive so you don't "need" the 0.5W resistor in this case but there's no harm in using it that I'm aware of.

[@kennmossman8701]

no difference in general a higher wattage resistor is less likely to drift or burn-out

[@goofygoober5841]

Really I can't be bothered doing this, will just add a random resistor and hope for the best.

[@Kaodusanya]

lol start from high and work my way down till its "stable" and lit.