Capacitance converter: pF, nF and µF

One capacitance in every unit at once: picofarads, nanofarads, microfarads, millifarads and farads, the marking code a part of that value carries, and the way it is usually written. Each unit is a thousand times the next, so the conversion is only ever a decimal point moving three places.

Fig 1 — 100 000 pF = 100 nF = 0.1 µF: the same digits in the same columns, with the decimal point three places further left for each prefix.

Capacitance value

Unit

Picofarads: 100 000 pF
Nanofarads: 100 nF
Microfarads: 0.1 µF
Millifarads · farads: 0.0001 mF · 0.0000001 F
Scientific notation: 1 × 10⁻⁷ F
Written the usual way: 100 nF
Three-digit marking code: 104 · 10 × 10⁴ pF

How this is calculated

Standard: BIPM — The International System of Units (SI Brochure, 9th edition), Tables 4 and 7

$1\ \text{F} = 10^{3}\ \text{mF} = 10^{6}\ \mu\text{F} = 10^{9}\ \text{nF} = 10^{12}\ \text{pF}$: SI Brochure Table 7: milli 10⁻³, micro 10⁻⁶, nano 10⁻⁹, pico 10⁻¹². Each step between the prefixes used for capacitance is a factor of 1000.
$C_{\text{pF}} = 1000\, C_{\text{nF}} = 10^{6}\, C_{\mu\text{F}}$: Going to a smaller unit multiplies the number by 1000 per step; going to a larger one divides by 1000. The digits never change, only the position of the decimal point.
$\text{code } d_1 d_2 n \;\Rightarrow\; C = d_1 d_2 \times 10^{n}\ \text{pF}$: The three-digit marking code, always counted in picofarads, from the capacitor code page's decoder. A value has a code only when its picofarad figure is two significant digits and a power of ten.

Assumptions

The conversion is exact; results are rounded at twelve significant figures only to remove binary floating-point noise, far below any capacitor's tolerance.
Values are printed in plain decimals, grouped in threes with a space for long integers as the SI Brochure describes, never in exponent form.
The marking code shown is the three-digit EIA-style code; tolerance letters, voltage prefixes and unit-letter forms are decoded on the capacitor code page.
The number is the nominal value. Tolerance, temperature and DC bias move a real part away from it; the conversion says nothing about them.

What a capacitance conversion actually does

Capacitance is measured in farads. The SI Brochure lists the farad among the units with special names, symbol F, equal to one coulomb per volt, and a farad is an enormous amount of capacitance for circuit work: the capacitors on a board are millionths and billionths of one. So every practical value carries an SI prefix, and the conversion between them is nothing more than the spacing of those prefixes. Table 7 of the brochure gives them: milli is 10⁻³, micro 10⁻⁶, nano 10⁻⁹ and pico 10⁻¹². Each step is a factor of one thousand, so moving from one unit to the next moves the decimal point exactly three places and changes nothing else.

That is the whole rule, and the figure above draws it. The same value, written in pF, nF and µF, has the same digits sitting in the same columns of place value; only the point moves. 100 nF is 100 000 pF because the point moves three places right, and it is 0.1 µF because it moves three places left. Going down a prefix, from µF to nF or from nF to pF, multiplies the number by 1000. Going up divides by 1000. No other factor ever appears between these units, which is why a conversion that produces a 10 or a 100 somewhere has gone wrong.

The brochure also settles how the answer is written. Prefix symbols "are attached to unit symbols without a space", so it is nF, not n F; the grouping "constitutes a new inseparable unit symbol"; and "compound prefix symbols, i.e. prefix symbols formed by the juxtaposition of two or more prefix symbols, are not permitted", so a value takes exactly one prefix. Between the number and the unit there is always a space: "the numerical value always precedes the unit and a space is always used to separate the unit from the number", which is why the site writes 100 nF rather than 100nF everywhere except in its own name.

Three spellings of the same part therefore turn up on the same bench: a schematic that says 100n, a datasheet that says 0.1 µF, and a component body printed 104. The first two are the same number with the point moved; the third is thecapacitor marking code, two significant digits and a power of ten, always counted in picofarads. The calculator gives all of them together, and says when a value has no three-digit code because its picofarad figure does not reduce to two digits and a power of ten.

SI prefixes used for capacitance

The five rows of the SI Brochure's Table 7 that capacitance uses, with one unit of each expressed in picofarads, computed by the calculator above. The column on the right is the conversion factor to the smallest unit, and each row is a thousand times the one above it.

Unit	Prefix	Factor	One of it, in pF
pF	pico	10⁻¹²	1 pF
nF	nano	10⁻⁹	1000 pF
µF	micro	10⁻⁶	1 000 000 pF
mF	milli	10⁻³	1 000 000 000 pF
F	(none)	10⁰	1 000 000 000 000 pF

pF to nF to µF conversion chart

Every E12 value from 1 pF to 82 µF in picofarads, nanofarads and microfarads, with its three-digit marking code and the unit it is usually written in, each row computed by the calculator above. Long integers are grouped in threes with a space, as the SI Brochure describes, and "neither dots nor commas are ever inserted in the spaces between groups". A dash in the code column is a value the code cannot express: below 10 pF the picofarad figure has fewer than two digits.

pF	nF	µF	Code	Usually written
1	0.001	0.000001	—	1 pF
1.2	0.0012	0.0000012	—	1.2 pF
1.5	0.0015	0.0000015	—	1.5 pF
1.8	0.0018	0.0000018	—	1.8 pF
2.2	0.0022	0.0000022	—	2.2 pF
2.7	0.0027	0.0000027	—	2.7 pF
3.3	0.0033	0.0000033	—	3.3 pF
3.9	0.0039	0.0000039	—	3.9 pF
4.7	0.0047	0.0000047	—	4.7 pF
5.6	0.0056	0.0000056	—	5.6 pF
6.8	0.0068	0.0000068	—	6.8 pF
8.2	0.0082	0.0000082	—	8.2 pF
10	0.01	0.00001	100	10 pF
12	0.012	0.000012	120	12 pF
15	0.015	0.000015	150	15 pF
18	0.018	0.000018	180	18 pF
22	0.022	0.000022	220	22 pF
27	0.027	0.000027	270	27 pF
33	0.033	0.000033	330	33 pF
39	0.039	0.000039	390	39 pF
47	0.047	0.000047	470	47 pF
56	0.056	0.000056	560	56 pF
68	0.068	0.000068	680	68 pF
82	0.082	0.000082	820	82 pF
100	0.1	0.0001	101	100 pF
120	0.12	0.00012	121	120 pF
150	0.15	0.00015	151	150 pF
180	0.18	0.00018	181	180 pF
220	0.22	0.00022	221	220 pF
270	0.27	0.00027	271	270 pF
330	0.33	0.00033	331	330 pF
390	0.39	0.00039	391	390 pF
470	0.47	0.00047	471	470 pF
560	0.56	0.00056	561	560 pF
680	0.68	0.00068	681	680 pF
820	0.82	0.00082	821	820 pF
1000	1	0.001	102	1 nF
1200	1.2	0.0012	122	1.2 nF
1500	1.5	0.0015	152	1.5 nF
1800	1.8	0.0018	182	1.8 nF
2200	2.2	0.0022	222	2.2 nF
2700	2.7	0.0027	272	2.7 nF
3300	3.3	0.0033	332	3.3 nF
3900	3.9	0.0039	392	3.9 nF
4700	4.7	0.0047	472	4.7 nF
5600	5.6	0.0056	562	5.6 nF
6800	6.8	0.0068	682	6.8 nF
8200	8.2	0.0082	822	8.2 nF
10 000	10	0.01	103	10 nF
12 000	12	0.012	123	12 nF
15 000	15	0.015	153	15 nF
18 000	18	0.018	183	18 nF
22 000	22	0.022	223	22 nF
27 000	27	0.027	273	27 nF
33 000	33	0.033	333	33 nF
39 000	39	0.039	393	39 nF
47 000	47	0.047	473	47 nF
56 000	56	0.056	563	56 nF
68 000	68	0.068	683	68 nF
82 000	82	0.082	823	82 nF
100 000	100	0.1	104	100 nF
120 000	120	0.12	124	120 nF
150 000	150	0.15	154	150 nF
180 000	180	0.18	184	180 nF
220 000	220	0.22	224	220 nF
270 000	270	0.27	274	270 nF
330 000	330	0.33	334	330 nF
390 000	390	0.39	394	390 nF
470 000	470	0.47	474	470 nF
560 000	560	0.56	564	560 nF
680 000	680	0.68	684	680 nF
820 000	820	0.82	824	820 nF
1 000 000	1000	1	105	1 µF
1 200 000	1200	1.2	125	1.2 µF
1 500 000	1500	1.5	155	1.5 µF
1 800 000	1800	1.8	185	1.8 µF
2 200 000	2200	2.2	225	2.2 µF
2 700 000	2700	2.7	275	2.7 µF
3 300 000	3300	3.3	335	3.3 µF
3 900 000	3900	3.9	395	3.9 µF
4 700 000	4700	4.7	475	4.7 µF
5 600 000	5600	5.6	565	5.6 µF
6 800 000	6800	6.8	685	6.8 µF
8 200 000	8200	8.2	825	8.2 µF
10 000 000	10 000	10	106	10 µF
12 000 000	12 000	12	126	12 µF
15 000 000	15 000	15	156	15 µF
18 000 000	18 000	18	186	18 µF
22 000 000	22 000	22	226	22 µF
27 000 000	27 000	27	276	27 µF
33 000 000	33 000	33	336	33 µF
39 000 000	39 000	39	396	39 µF
47 000 000	47 000	47	476	47 µF
56 000 000	56 000	56	566	56 µF
68 000 000	68 000	68	686	68 µF
82 000 000	82 000	82	826	82 µF

Read any row across and the digits never change: 4700 pF, 4.7 nF and 0.0047 µF are the same 47 with the point in three places. The usual column follows one convention, the unit that puts the number between 1 and 1000, which is what engineering notation does and what the calculator's "written the usual way" row reports. Plenty of datasheets and catalogues break it, quoting 0.1 µF rather than 100 nF or 1000 pF rather than 1 nF; both are correct, and the chart is there so neither has to be worked out again.

Worked example: 100 nF, 11 nF and 4.7 µF

The default is the site's namesake, 100 nF, and two more values that people type into a search box more than they should have to.

100 nF   × 1000  = 100 000 pF      ÷ 1000 = 0.1 µF      code 104  (10 × 10⁴ pF)
11 nF    × 1000  = 11 000 pF       ÷ 1000 = 0.011 µF    code 113  (11 × 10³ pF)
4.7 µF   × 1000  = 4700 nF         × 1000 = 4 700 000 pF   code 475  (47 × 10⁵ pF)
22 pF    ÷ 1000  = 0.022 nF        ÷ 1000 = 0.000022 µF    code 220  (22 × 10⁰ pF)

The first line is why the site is called what it is: 100 nF is the most common capacitor on any board, and it answers to three names. Thewhy 100 nF article is about where that value came from and where it stops working as a capacitor. The last line shows the other direction: a small value becomes a long decimal in microfarads, which is why nobody writes 22 pF as 0.000022 µF, and why a calculator that prints 2.2e-5 has not really converted it.

Where the converted value stops being the real one

The conversion is exact; the capacitor is not. Moving a decimal point loses nothing, but the value printed on a part carries a tolerance letter, and a ceramic's capacitance depends on the voltage across it. A 100 nF X7R part at its rated voltage can hold a fraction of its marked value, which theDC bias articlemeasures. Converting 100 nF to 0.1 µF is right; assuming either number is what the circuit sees is a separate question.

The code has limits. The three-digit marking needs two significant digits in picofarads, so it cannot express 1.5 pF, 1234 pF or anything with three significant figures. Parts like those are marked in full or with a unit-letter form, 4n7 or 1p5, which thecapacitor code decoder reads.

Floating point. A computer asked for 0.1 × 10⁻⁶ × 10⁹ returns 100.00000000000001, not 100, because 0.1 has no exact binary form. The calculator rounds that noise away at twelve significant figures before printing, which is far below the tolerance of any capacitor ever made, and prints in plain decimals rather than exponent form so the answer can be read without converting it again.

Common capacitance conversion mistakes

Moving the point the wrong way. A smaller unit means a bigger number: 100 nF is 100 000 pF, not 0.1 pF. If the number shrank on the way to a smaller unit, the point went the wrong way.
Moving it the wrong distance. Every step between pF, nF, µF, mF and F is three places. Six places between pF and µF, nine between nF and F; never one or two.
Confusing milli and micro. Table 7 gives them different symbols, m for 10⁻³ and µ for 10⁻⁶, and a thousand times between them. A 1 mF part is 1000 µF, a large electrolytic, not a small ceramic.
Reading a code as a value. 104 is not 104 pF; it is 10 followed by four zeros, 100 000 pF. The last digit is a count of zeros.
Stacking prefixes. Each value takes one prefix, as the SI Brochure requires; a picofarad is never a micro-microfarad in current notation, and a nanofarad is never a milli-microfarad.