10000 pF - so many zeros

Question

Why are 10 nF capacitors sometimes (usually) specified as 10000 pF?

Why are we trying so hard to avoid nF? Seems unnecessary and error prone.

Note: Question also relates, of course, to 1 nF vs 1000 pF - of which there are four 1 nF ceramics on Digi-Key, versus nearly 17,000 1000 pF (though Digi-Key properly returns either in the search). The point of the question is the intentional avoidance of nF.

Spehro has given you the perfunctory answer. There is a special code for specifying ceramic capacitors that was developed so long ago I can't remember when. If that's sufficient, then it is. The other reason is that when you are thinking in terms of crystal oscillators (developed aggressively during WW II) or RF or coil parasitics, you are often *mentally* thinking in picoFarads all the time. It's just where your brain is at. So the code itself reflects that mindset. NanoFarads were just "lots of picoFarads." — jonk, Mar 26 '22 at 21:42
@jonk It may be true, but it sure is buried under lots of characters in there. The first place people will read is the "readable" 3rd line. After all, it's not like they have a stamp which is difficult to make in more than one physical form -- it's printing, it's cheap, it's not necessarily RF, and it's no longer the 40's. Maybe I'm just particularly grumpy right now, but I agree with OP. — a concerned citizen, Mar 26 '22 at 21:45
@aconcernedcitizen It's the history of ceramics, to me. Perhaps because I lived it? I get that someone much younger and exposed to a different world may not place the same emphasis I may. But I have grown up keeping little boxes of ceramics around and picking them out. Small ones were a few pF. Big/fat ones were likely in the hundreds or even thousands. But the nomenclature applied to all of them in the same way and to a person thinking of ceramics "as a tangible thing you can put your hands on and feel and recognize" (plus mica) and not just a concept, the standard makes sense. — jonk, Mar 26 '22 at 21:48
@aconcernedcitizen Just to place some juxtaposition into the mix, [here is a variable capacitor sitting here on my desk](https://i.stack.imgur.com/j3eCN.jpg) that varies up to about 400 pF. But to me it is NOT a ceramic cap. So I would be entirely open to having a different code for specifying these beasts. It only turns out by happenstance that the variable range of these works out to the same region that ceramics are often found. But I think of it differently than I do a ceramic. So a different coding technique for them would not phase me at all. — jonk, Mar 26 '22 at 21:54
@jonk I understand your reasoning, and even a rather middle-aged like me has dealt with old TVs & co and with the afferent saving boxes. But this is not something that needs backwards compatibility, and `10 nF` is a much more clear and error-free than `10000 pF`. Eh, I'm probably being subjective, given that my eyes are not exactly hawk-like. :-) — a concerned citizen, Mar 26 '22 at 21:56
@aconcernedcitizen I think GT is providing still more to the picture. Perhaps that's where you can rest more easily. I am just old enough now to have lived through these periods and so the nomenclature is fine. As GT writes, the SI orthodoxy was rolled out later on and has not yet been imposed by fiat upon all manufacturers for all products. I'm okay with still using a 'cgs' oersted instead of an 'SI' amp/meter (an an implied \$4\pi\$ constant difference), for example. I can survive old units. — jonk, Mar 26 '22 at 22:00
There might be historical and cultural reasons that varied between companies and their geographical location. There was a time period where you just don't see nanofarads in schematics. Everyhing was either in microfarads or picofarads. 1 and 0.1 and 0.01 without any other markings were in microfarads and smaller capacitances were marked like 22p or 1000p for picofarads. The capacitor type/material may also have played a role, 0.001 might be higher K ceramic or plastic film while 1000p might be lower K ceramic. — Justme, Mar 26 '22 at 22:19
@jonk As I said, I can understand the reasoning, but both GT and you seem to indirectly reinforce the idea of backward compatibility. This usually spells "we've doing it like this for ages, just comply" (not that hash). If I were to choose between an old habit, and an easier reading and less error-prone, I wouldn't even hesitate for the latter. Habits can be formed anytime, improvements are not so often. Don't misunderstand me, I, too, have habits, but if they would have less value than something new, I wouldn't try to keep them to the detriment of the improvements. But that's just my POV. — a concerned citizen, Mar 26 '22 at 22:30
@aconcernedcitizen Sure. I think we can rest there. *Home* is where you are comfortable. Which means *memories*. There's also moving towards good standards for mutual communication across culture, time, and place. So I get that, too. — jonk, Mar 26 '22 at 22:35
@jonk And nobody will ever take your memories, or your comfort with them, but those are personal. Should they be everyone else's, too? That people lived like that, or, that there are who still do, good for them, but do the rest have to live like that, too? Yes, after a life of habit one gets more "static", and with less will to fight, but there's no need to force others to one's ways if the others find something else that's better (for them). That's what I was trying to say. I liked the discussion and I hope you don't think I was pointing the finger or being selfish (none), but ... — a concerned citizen, Mar 26 '22 at 23:04
...I'll delete these tomorrow since they're only (my) opinions on the subject; they add nothing to the topic. — a concerned citizen, Mar 26 '22 at 23:05
@aconcernedcitizen I will also delete mine then. Enjoyed the discussion. :) We live in different times, exposed to different fads, grow up in different cultural contexts, etc. I would not take away from me those things that created me (until I die.) And about half of what science is about is in finding a language for expression of knowledge that transcends all of these, so that someone 1000 yrs ago and someone 1000 yrs from now can read what I write today and replicate my results. This loses something in the exchange. But gains something too. Engineering is more about science. So you win! — jonk, Mar 26 '22 at 23:17
@jonk I'm sorry for replying, it's not about having the last word, but I wasn't competing, so there's nothing to win. And since my point was to avoid forcing others, I can't (and won't) force you to have my views. They're just views. And your reply seems to be on the apologetic side, which means somewhere I gave exactly the impression that I didn't want. I apologize for that. If I could summarize, I'd say "to each his own", as dry and vague as it may sound. So if you have your views, ok, if I have mine, same ok, your happen to coincide with GT's, mine with OP's. Life goes on. — a concerned citizen, Mar 26 '22 at 23:32
@aconcernedcitizen I was just teasing you. But since you don't live in my culture you cannot tell. I got exactly where you were coming from. But mine just passed over your head and you worried. No worries. Really! — jonk, Mar 26 '22 at 23:41
@jonk & aconcernedcitizen You guys are the best there are. Fwiw, I knew, of course, the general answer to my own question. Your discussions on the value of maintaining legacy hits the heart of what I had only vaguely alluded to (to avoid opinion closure). Full applause; fascinating discourse. Shame to have it deleted. — Blair Fonville, Mar 26 '22 at 23:53
I’ve never seen 10 or 100nF capacitors specified in pF. Sometimes you see 100nF as 0.1μF. — Michael, Mar 27 '22 at 06:53
@BlairFonville If you want to preserve the comments then you'll need to let aconcernedcitizen know in clear terms. Whether or not he decides to keep them is his own choice, still. But I'll keep mine around if he decides to keep his. Otherwise, there's no point. But thanks for the kind words. They're pleasant to hear. — jonk, Mar 27 '22 at 08:10
@BlairFonville There may be some points, here and there, but it's still a bucket of comments filling up space. If you think they add anything else than a thematic banter, I won't delete them, but that will have to be as jonk says: with your explicit green light... and moderators', of course. — a concerned citizen, Mar 27 '22 at 08:28
@aconcernedcitizen - Hi, FWIW (and I'm only one mod) your exchange of technical experiences with jonk (with you both being kind & respectful of different opinions) adds value to the site. Alas, as you recognise, it doesn't fit the Q&A mission here. My recommendation is that instead of you both deleting your contributions, I propose to move those comments into a chatroom which I then freeze (thereby preventing anyone thinking it's active for more chat) to effectively archive them. (Comments by others left untouched). That way nothing is lost, I would add a link here to that chatroom. Thoughts? — SamGibson, Mar 27 '22 at 21:43
@SamGibson If there are no other objections, it sounds fine by me. — a concerned citizen, Mar 28 '22 at 07:28

GT Electronics · Accepted Answer · 2022-03-27T20:17:26.337

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It's historical. Capacitors were difficult to make by rolling paper (long before polymer films were available). There were two categories, rolled (around a microfarad range labeled "M") and flat (around a millionth of a microfarad labeled "MM") in the old-old days (early days of radio). Capacitors have long been either "MF" (microfarad), or "MMFD" micro-microfarad (now known as picofarad).

The prefixes of nano and pico (from SI standardizations of the 1960s) are long after the first capacitors were sold.

Note: as you noticed, the nanofarad never really caught on as a unit of measure for some manufacturers and neither has the millifarad. 10,000 µF is a common value.

edited Mar 27 '22 at 20:17

answered Mar 26 '22 at 21:48

GT Electronics

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Re *"the nanofarad never caught on as a unit of measure"*: I don't know. 100 nF is pretty common for decoupling capacitors. – Peter Mortensen Mar 27 '22 at 13:26
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There seems to be a disconnect between designers and suppliers, I've seen many designs specify capacitance in nanofarads, but I don't think i've ever seen any major supplier sell them that way. Suppliers seem to use picofarads for values below 100nF and fractional microfards for 100nF and larger. – Peter Green Mar 27 '22 at 14:02
I remember being impressed they could put so many bicycles in a small package, until I learned the M was for micro-, not for mega-. – Mast Mar 27 '22 at 16:23
@mast Bicycles? I'm not sure if this was a typo or a joke that I'm not getting. I want it to be a joke - please explain (or give a hint) – GT Electronics Mar 29 '22 at 04:22
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@GTElectronics Fahrrad is German for bicycle. – Mast Mar 29 '22 at 15:13

score 7 · Answer 2 · answered Mar 26 '22 at 21:36

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Have a look at the part number:

"103" = 10,000

answered Mar 26 '22 at 21:36

Spehro Pefhany

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Thanks Spehro. I suppose that’s the crux of the answer, though… so what? It makes sense as an abbreviation in the marking and P/N, but not so much for BOMs, distributor listings, schematics, etc. There are lots of examples of how we abbreviate markings for smd parts that are otherwise outside of our typical vernacular. – Blair Fonville Mar 26 '22 at 21:48
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You can still use nF on your schematics, of course, and I imagine most of us do so. I guess it's a trade-off. It also helps with sorting. I think most parametric lists get nF/pF right, but things like ppm/ppb get mis-sorted regularly. We mix 6.3mm or 6.35mm vs. 1/4" and various other things regularly, this seems like a pretty minor inconvenience. I guess 22,000,000pF might be a bit too far. – Spehro Pefhany Mar 26 '22 at 21:51
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Yeah, sorting may be something I guess (+1 for that and for your answer in general). Yes, you can use nF in schematics, but our librarians typically just use whatever is in the part’s specifications - so 10000 pF is normally entered into the cad’s part. Sometimes, depending on who builds the part’s lib, they’ll go with 10 nF. So we end up with a mix. – Blair Fonville Mar 26 '22 at 22:08
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Just be thankful you don't often see millimicrofarads much these days... – Mar 27 '22 at 02:14
Does 103=10,000 because it's 10 followed by three zeros? 104=10⁴ would also work. – Andrew Leach Mar 27 '22 at 08:07
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@AndrewLeach It’s a standard convention in electronics: the first two digits represent the numerical value, the third one is the exponent of the base-ten multiplier, and the value is given in pF. So, 224 means 22×10⁴ pF. Similar markings apply to resistors. – Massimo Ortolano Mar 27 '22 at 08:42

score -2 · Answer 3 · answered Mar 27 '22 at 00:10

Why are we trying so hard to avoid nF? Seems unnecessary and error prone.

"We"? "We" are not trying anything. Let's call it like it is. DigiKey is. This question should be addressed to them, not to the general public. It's their arbitrary choice. Really. We can only second-guess them. Not everything in DigiKey's database makes most sense from an electrical engineer's standpoint, that's for sure. At least their search is clever enough to substitute their canonical value for 10NF. You'll find that the search results for 10NF and 10000PF are identical, at least from some search locales. For some reason this behavior seems localized, or at least was - I was bitten by that a year or two ago.

Other online distributors that copy DigiKey's approach without much thought just replicate this. You could ask them as well.

That’s a fair point. But if you look at the Kemet datasheet for the part that I referenced (via photo), they list up to 82000 pF before transitioning to 0.1 uF: https://content.kemet.com/datasheets/KEM_C1023_X7R_AUTO_SMD.pdf — Blair Fonville, Mar 27 '22 at 00:18
They do it because everyone does it, and never asks why. I guess they like numbers that look big on paper... — Kuba hasn't forgotten Monica, Mar 27 '22 at 17:04

score -7 · Answer 4 · answered Mar 27 '22 at 12:51

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10 nF and 10000 pF are a bit different, and it is necessary to mark the difference. It is similar to shopping for potatoes at the groceries. Let's say someone needs to buy 15 kg of potatoes in one go, but has a long way back home. What would that person do? Buy 15 kg of small potatoes, of course, because 15 kg of large potatoes would be too heavy to carry back home. If items at groceries were labeled in the same manner as those capacitors, the labels would be "15000 g" for small potatoes, and "15 kg" for large potatoes.

Likewise, you use 10000 pF capacitor if you need a certain capacitance and the specification of a small capacitor, and you use 10 nF one if you need the same capacitance but also somewhat a more grand one.

Hope this helps.

answered Mar 27 '22 at 12:51

Chad Branzdon

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It doesnt matter if the potatoes are big or small if they weigh the same it will be equally hard to carry them home. – Jun Seo-He Mar 27 '22 at 12:55
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Your analogy doesn't seem to fit well. `10 nF` and `10000 pF` are _exactly_ the same, just the notation differs. Whereas small and large potatoes differ quite a bit. – Velvel Mar 27 '22 at 13:17
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@Seir Correct, 10 nF and 10000 pF are exactly the same. But 15 kg and 15000 g are also exactly the same. However, a small potato weighs less than a large one. Large potatoes are much heavier, that's my point. – Chad Branzdon Mar 27 '22 at 13:58
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I can’t tell if this answer is supposed to ironic or not. – Blair Fonville Mar 27 '22 at 14:49
I really appreciate your answer - and your willingness to perform comedy in front of the second-most* difficult of audiences (engineers). I had a good laugh! Thanks. *(children are the most difficult audience for comedians). – GT Electronics Mar 29 '22 at 00:34

10000 pF - so many zeros

4 Answers4