The capacitance prefix ladder
Capacitance spans a huge range — from single picofarads in RF circuits to whole farads in supercapacitors — so every value is written with an SI prefix, and each step on the ladder is a factor of a thousand:
1 F = 1,000 mF = 1,000,000 µF = 10⁹ nF = 10¹² pF
The three you will meet constantly are µF, nF, and pF. The conversions worth internalizing: 1 µF = 1,000 nF, 1 nF = 1,000 pF, and the perennial one, 0.1 µF = 100 nF = 100,000 pF — the standard bypass capacitor written three different ways.
Common values, all three ways
| µF | nF | pF | Marking code |
|---|---|---|---|
| 0.00001 | 0.01 | 10 | 100 |
| 0.0001 | 0.1 | 100 | 101 |
| 0.001 | 1 | 1,000 | 102 |
| 0.01 | 10 | 10,000 | 103 |
| 0.1 | 100 | 100,000 | 104 |
| 1 | 1,000 | 1,000,000 | 105 |
| 10 | 10,000 | 10⁷ | 106 |
Why datasheets mix units
Convention, mostly regional and historical. American schematics traditionally jump straight from µF to pF, writing 0.01 µF where a European schematic says 10 nF — the nanofarad barely existed in older US practice. Old capacitors and motor-start caps are often marked MFD or mfd, which confusingly means microfarads (µF), not millifarads. And ceramic capacitors usually carry a three-digit code (pF digits plus a multiplier) rather than any unit at all — 104 is 100,000 pF, which is 100 nF, which is 0.1 µF: one part, three spellings, one code.
Reading between the lines
A rule of thumb for which unit a designer meant when the marking is ambiguous: electrolytics are almost always µF, film capacitors nF, and small ceramics and RF parts pF. If a value looks absurd in one unit — a "4700 µF" ceramic the size of a grain of rice — it was probably meant in a smaller unit.
Related tools: the capacitor code calculator decodes the 104/473K markings themselves, the series & parallel capacitor calculator combines values, and the reactance calculator tells you what a capacitance actually does at a given frequency.