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You are here: Home / Basic Electronics / Capacitor Values – Prefixes, Standards and Calculations

Capacitor Values – Prefixes, Standards and Calculations

July 3, 2014 By Øyvind Nydal Dahl 51 Comments

There are some standard capacitor values that have developed over time. To find the value you need for your circuit you need to know how to deal with prefixes. And you need to know how to calculate capacitor values.

Electrolytic capacitor

If you have looked for capacitors, you have probably seen many different letters and weird values. Like 0.47 \mu F or 22 pF. It is a bit confusing, but it’s easy to learn what it means.

In this article you will learn the most standard capacitor values, the prefixes used and how to calculate a capacitor value for your circuit.

The Prefixes

Capacitor values are given in Farad. The symbol used is F. It’s named after the English physicist Michael Faraday.

But 1 Farad is pretty big. So capacitor values are usually given with a prefix. Often you are going to work with capacitors values in pico-farads to micro-farads.

To make this simpler to deal with, I’m going to show you how the prefixes work.

A prefix is something you put in front of the farad symbol (F). It tells you what you have to multiply the number with. For example 1 pF means 1 F multiplied with the prefix p which is 10^(-12). It can also be written 0.000000000001

Here is a table with the most common prefixes for capacitors:

Prefixes
1 F 10^{0} F 1 Farad
1 \mu F 10^{-6} F 0.000001 Farad
1 nF 10^{-9} F 0.000000001 Farad
1 pF 10^{-12} F 0.000000000001 Farad

Which Capacitor Values Are There?

Capacitors are available in a lot of values. Over time, some standard values have emerged. Here is a table from rfcafe.com with the most commonly found capacitor values:

List of standard capacitor values from rfcafe.com
Table from rfcafe.com

How Do You Choose Capacitor Values?

You choose a capacitor value by using the RC time constant:

\tau = R * C

This constant gives you the time it takes for a voltage in an RC circuit to go from 0% to 63% of its full value.

You can use this time constant to calculate the cutoff frequency in a filter, or just how long a delay will be in a blinking light circuit.

Calculating Capacitor Value For A Circuit

Low-pass filter using a capacitor and a resistor
Low-pass filter using a capacitor and a resistor

Let’s say we want to make a low pass filter with a cutoff frequency of 15 kHz. The formula for calculating cutoff frequency is:

f_{c} = \frac{1}{2 \pi RC}

and by switching it around we can calculate for C:

C = \frac{1}{2 \pi R f_{c}}

Now, let’s choose to use a 1k resistor. This gives us:

C = \frac{1}{2 * 3.14 * 1000 \Omega * 15000 Hz} = 0.000000011 = 11 nF

So to get a cutoff frequency of 15 kHz, we need a 1k resistor and a 11 nF capacitor.

Different Types of Capacitors

To make everything more confusing, capacitors come in many different types. I have written a simple guide on how to choose a capacitor type that you should check out.

There is no need to memorize these things. Just bookmark this page and you’ll have easy access to it later on. When you have used the prefixes and the formula enough times, you will automatically remember them.

Return from Capacitor Values to Electronic Components Online

Filed Under: Basic Electronics

Reader Interactions

Comments


  1. Jonathan says

    September 30, 2014

    Hey Oyvind,

    I am trying really hard to understand what’s on the page, but it’s really hard to when all the pictures aren’t loading. I don’t know what’s happening. It only happens on this one.

    Reply

    • admin says

      September 30, 2014

      Hmm. that’s weird. They are loading for me…

      Oyvind

      Reply

  2. Evan says

    December 26, 2014

    Hello there Oyvind,

    I was wondering about the RC time constant. What is R and what is C? So far capacitors really have me confused about whats what.

    Reply

    • admin says

      December 30, 2014

      Hi Evan,

      R is resistance given in Ohms.
      C is capacitance, given in Farads.

      Cheers!
      Oyvind

      Reply

    • Leo Zappa says

      December 12, 2018

      Think about it like filling a container with water. The capacitor stores electrons. A resistor in series with the capacitor will impede the flow, extending the time it takes to reach full capacity.

      Reply

  3. Sapna Razdan says

    February 18, 2015

    if i need a 400V capacitor, can i use 350V or 450V capacitor instead of 400V.

    Reply

    • admin says

      February 19, 2015

      Hi,

      400 volt is how much voltage the capacitor can handle. So you want 450V at least.

      Cheers!
      Oyvind

      Reply

      • George Constanza says

        May 26, 2015

        Is there a minimum value of voltage that a capacitor can work with?

        Reply

        • admin says

          October 1, 2016

          No, there isn’t any minimum voltage.

          Reply

  4. Ricky Ho says

    September 25, 2016

    Hi.

    I would like to introduce the application of a capacitor to the kids and I think a simple windmill project should be the best example to highlight the application.

    I need a small capacitor in a simple electric circuit of a self-made windmill. I am going to use 2 x 1.5v battery for the project. Appreciate your advise on what type of capacitor to use for this project as I do not know how to choose one. Thank you.

    Reply

    • admin says

      October 1, 2016

      Hi Ricky,

      It’s difficult to say without knowing more. What is the purpose of the capacitor in this application?

      Reply

  5. Barry Ng says

    October 19, 2016

    Hi, I seriously don’t know what page mean can you give a simpler explanation of all his page means like starting from the prefixes and the calculation.

    Reply

    • Barry Ng says

      October 19, 2016

      Hi , sorry about the typo above. I was saying that can you give me a simpler explanation at this page I don’t understand what the prefixes and the calculation means.

      Reply

      • admin says

        October 19, 2016

        Hey Barry,

        Prefixes are an shorter way to write numbers. For example “kilo” means 1000 and uses a “k” as a symbol. This means instead of writing 10000, I can write 10k.

        Best,
        Oyvind

        Reply

        • Barry Ng says

          October 19, 2016

          What is the table from rfcafe.com for? And what is the use of knowing this? Is it if we know how to calculate then we know which capacitor will be the best in our circuit?

          Reply

          • admin says

            October 19, 2016

            Yes, exactly.


  6. Barry Ng says

    October 19, 2016

    Then the table from rfcafe.com for?

    Reply

    • admin says

      October 19, 2016

      It shows the most commonly found capacitor values. If you for example have calculated that you need a capacitor of 17µF, you can check if that exists in the table. Since it doesn’t you have to find another way of doing it or go with one of the values that are listed.

      Reply

      • Barry Ng says

        October 19, 2016

        Tq

        Reply

        • Barry Ng says

          October 19, 2016

          Can I know what is the symbol equal to R * C? And please explain what it mean.

          Reply

  7. Leo says

    October 21, 2016

    Hi, can I know the part of “how do you choose capacitor values” in this page. What is the equation of that first symbol before equal R times C? And also explain what did it mean? Is it voltage?

    Reply

    • admin says

      November 4, 2016

      It’s called “tau”. It’s the time constant. This constant gives you the time it takes for a voltage in an RC circuit to go from 0% to 63% of its full value.

      Reply

  8. Ibn Ishaq says

    October 23, 2016

    please can you explain what cut off frequency means.i tried google searching but i got confused even more.
    i love your writing style though….keep up the good work!

    Reply

    • admin says

      November 4, 2016

      In what context?

      In a low-pass filter for example you only allow frequencies below the cutoff frequency to go through.

      Best,
      Oyvind

      Reply

  9. Billy says

    December 31, 2016

    Hi, in your exemple, how did you end up with 15 000Hz that’s the only part I don’t get. I don’t know what a low-pass filter is could you explain?

    Thanks

    Reply

    • Billy says

      December 31, 2016

      I’m asking because I want to make a hand crank flashlight using a 6V and 0.04A Dynamo, 3,1V LEDs, an interupter/switch and a capacitor but I don’t know which capacitor to choose. So I would like to figure it out.

      Thanks

      Reply

      • admin says

        January 3, 2017

        Hi Billy,

        For your project, you don’t need a low-pass filter, so just ignore that part.

        It’s hard for me to say anything about the size you need since I don’t what you are using the capacitor for.

        Best,
        Oyvind

        Reply

        • Billy says

          January 7, 2017

          I need a capacitor to store the energy from my dynamo. Does that make sense? I want to be able to use my flashlight without having to continusly rotate the motor. Just like hand crank flashlights that we can purshase. (Its doesn’t have to be as efficient though)

          Thanks

          Reply

          • admin says

            January 9, 2017

            Ah ok, I understand. Capacitors normally store very little energy. But you should look into super capacitors. They can store more energy.


  10. Philip B says

    February 7, 2017

    I’m trying to repair the power supply circuit in a transceiver that I have. I know I need a 3300 uF 70 VDC electrolytic capacitor, but every time I go to a website to FIND one, I’m also asked what tolerance I need, ripple current, ESR, ROHS compliant,etc. Do I need to worry about these values or not?

    Reply

    • admin says

      February 10, 2017

      Hey Philip,

      The most important for you is to find a capacitor that has 3300 µF and a voltage rating of 70V or more. Don’t worry about the other stuff.

      Best,
      Oyvind

      Reply

  11. Zeljko Vukosavljev says

    February 23, 2017

    Hi,

    if I want LED 3V blinking once per second, using this scheme, but the input voltage is 9v, what are the values for R and C. If you can write formulas and how you got those results. Thank you.

    Zeljko

    Reply

    • admin says

      February 24, 2017

      Hi,
      I don’t know which circuit you are referring to. There are no blinking LEDs in this article..

      Best,
      Oyvind

      Reply

      • Zeljko Vukosavljev says

        March 1, 2017

        Hi,
        I think the circuit from the text above, if I put on the output LED 3V and input voltage of 9V.

        Reply

        • admin says

          March 9, 2017

          Do you mean the filter circuit? It will not make the LED blink. Here’s some circuits to blink an LED:
          https://www.build-electronic-circuits.com/blinking-led-circuit/

          Best,
          Oyvind

          Reply

          • Zeljko Vukosavljev says

            March 13, 2017

            OK, thanks.

            Zeljko


  12. Fabricio baca says

    April 17, 2017

    … just reading through. Interesting

    Reply

    • Jamey Hall says

      January 20, 2019

      I took couple yrs of electronic engineering. .1/2
      Back,25yrs ago as a technical student course my freshman/soph. Yr.
      I really enjoyed electronics, never could afford all the highends and newer technology tht aspired thn…so the course helped me with tht, made a few dollars here and there as well as i was trying to fix every car stereo, with missing plug and solder my own pig out ..and burnt units.. (lack of sense, of most..) dollars was my lack so stayed close to those fools lol…amps were ALWAYS just a burnt curcuit…quik soldered jump wire and i was in there. I would b bumping to it same day…sry carried away for sec, i ended up going a whole nother direction.
      For all my yrs, past few yrs started picking up flatscreens (tv) first couple nothing wrong, (prob jus ws n need of a reset) cause once booted up no sigins of anything. So ofcourse tht got the ball rolling again for me, i forgotten until tht moment tht i had ever heard words solder/flux/resistance. ..ac/dc lol smh well not all rest was so lucky as first (it my calling ibelieve) well starting back i didnt remember anything really, first few i spotted problems by merely eyes only, hot joints, burn tru, no standby voltage, fuse, dirty ribbon connections…buldging….not knowing where came from…started researching again to learn…i have been better with only my eyes…until i ran cross your charts, descriptions, and explanations…first and third person on delivering this complicated algebraic shockwaves of colors, numbers, letters, sy.bols, lol u have got me lined back up with a clear line of sight now….i was ready give my passion up again! Sry dnt know if im supposed to drop this here but i am did t want to lose ya and not share my story! Few of those past reads they seemed confused. ..but knew tht feeling to well, you are a gent and a scholar! ! Ty so, frm me and for thm….ur a good person for what udo here!!!! Thnx…

      Reply

  13. MD. Rakibul Islam Prince says

    June 7, 2017

    suppose I am using a 24v DC power supply.then as a decoupling capacitor which capacitance/volt
    should I use?

    Reply

  14. Thomm says

    August 24, 2017

    i want to use a capacitor for my 125cc local motor cycle!!!
    my batt is good and my regulator rectifier is good, but i install a 60w led light
    1 as back up of my headlight 18w
    and d other 2 is in d rear side
    for increasing my illumination when i travel at night!
    can i use capacitor for my 3 led light as a current smooth protection
    and at d same time for helping my batt life…!
    sir how to calculate of capacitance that i need in d future?
    thank you very much
    more power!!!
    d name is Thomm
    from d Philippines…

    Reply

  15. Hein says

    December 30, 2017

    Hi, what can I replace a 78 faret ceramic disc cap with? The application is in a tv power supply circuit. The value on the cap is u78Z .

    Reply

    • admin says

      January 22, 2018

      Ceramic disc caps are very easy to find, so just replace it with another one.

      Reply

  16. John says

    January 20, 2018

    Hi please help! Let say I am required to select a capacitor value of 5.8nF for my circuit, but the only available capacitors in my workshop are 6.8nF and 4.7nF. Which value should i choose?

    Reply

    • admin says

      January 22, 2018

      Hi, that depends on what it’s for. If you don’t know the calculations just pick one and see if it works. If it gives you a bad result, try the other one.

      Best,
      Oyvind

      Reply

  17. C.R.Joshi says

    February 12, 2018

    Hon.Being inspried through your explanation,I am trying to
    figure out as if we have a circuit
    Of 220 volt supply AC and in circuit we need 50 volt DC in such a case how to find out required value capacitor like it’s
    micro farade,it’s voltage rating,and if needed it’s charge.
    How to calculate and figure out exact value capacitor we need?
    CRJ.

    Reply

  18. Thato says

    February 15, 2018

    Hi ……

    eeeeh am give Resistor as 100ohms , capacitor as 10ohms , inductor as 10ohms and de supply voltage is 200v ……plz help on hw to calculate de value of capacitor nd inductor …!!!

    Reply

  19. Cameron Nicoll says

    October 15, 2018

    Hello Oyvind,
    I have a circuit board that I want to repair but 3 capacitors have blown and were taken out of the board so I have no reference.

    Is there any way of knowing what capacitors I can use to get the board running?
    No, I do not have a schematic.

    Reply

    • admin says

      October 17, 2018

      There are ways to make a good guess at least. First of all – what type of circuit do the capacitor belong to?

      A microcontroller circuit, connected to the power pin of the microcontroller? Often 100nF.

      Connected to some kind of component with writings on them? Find the datasheet of the component and see if the datasheet tells you anything about its capacitors.

      Best,
      Oyvind

      Reply

  20. Bradley Ward says

    August 13, 2019

    If someone wanted to choose a capacitor for use as a DC blocker on a standard electric line, (120 VAC, 60HZ) in order for the capacitor to go bad before allowing the device to be damaged by, say lightning, but not restrict the incoming electricity during normal use, how would you choose the proper Farad rating in that case, as you couldn’t use the R*C multiplication, since there wouldn’t be a resistance in the line large enough to use the formula, correct?

    Reply

  21. Panagiotis says

    September 15, 2020

    Hello Oyvind,

    I want to use a capacitor in a simple circuit to blink a led by using a switch and a LED. Nothing else except a power supply of 5v from an arduino.
    How can I calculate the value of the capacitor?
    How can I use your formula in a DC supply? Is there still a frequency here and if yes how can I find it?

    Thanks a lot,
    Panos

    Reply

    • admin says

      September 16, 2020

      Hi Panos, how to calculate the capacitor value depends on your circuit. I don’t see how you can blink an LED with just a switch (unless you’re planning to use a digital output from the Arduino with blinkled code). So if you can post a link to the circuit you’re planning to use, it would be easier to say.

      Best,
      Oyvind

      Reply

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