| Unit | Symbol | Equivalent | Common Applications |
|---|---|---|---|
| Farad | F | Base unit | Supercapacitors, very large energy storage |
| Millifarad | mF | 10-3 F = 1,000 μF | Large electrolytic capacitors, power filtering |
| Microfarad | μF | 10-6 F = 1,000 nF | Power supply filtering, coupling, timing circuits |
| Nanofarad | nF | 10-9 F = 1,000 pF | Signal coupling, bypass capacitors |
| Picofarad | pF | 10-12 F | RF circuits, high-frequency applications |
The first two digits represent significant figures, and the third digit is the multiplier (power of 10).
A number followed by a letter, where the letter represents a multiplier.
Includes voltage rating, capacitance value, and tolerance in one code.
Common EIA voltage codes used in combined capacitor markings:
The dimensional formula for capacitance is [M-1 L-2 T4 I2].
Capacitance is defined as the ratio of charge (Q) to voltage (V): C = Q/V
Since charge has dimensions [I·T] and voltage has dimensions [M·L2·T-3·I-1], capacitance has dimensions:
C = [I·T] / [M·L2·T-3·I-1] = [M-1·L-2·T4·I2]
| μF (Microfarad) | nF (Nanofarad) | pF (Picofarad) | Common Applications |
|---|---|---|---|
| 1000 μF | 1,000,000 nF | 1,000,000,000 pF | Large filter capacitors |
| 470 μF | 470,000 nF | 470,000,000 pF | Power supply smoothing |
| 220 μF | 220,000 nF | 220,000,000 pF | Audio coupling |
| 100 μF | 100,000 nF | 100,000,000 pF | Decoupling capacitors |
| 47 μF | 47,000 nF | 47,000,000 pF | Timing circuits |
| 22 μF | 22,000 nF | 22,000,000 pF | Audio applications |
| 10 μF | 10,000 nF | 10,000,000 pF | General purpose |
| 4.7 μF | 4,700 nF | 4,700,000 pF | Signal coupling |
| 2.2 μF | 2,200 nF | 2,200,000 pF | Filter circuits |
| 1 μF | 1,000 nF | 1,000,000 pF | Bypass capacitors |
| 0.68 μF | 680 nF | 680,000 pF | AC coupling |
| 0.47 μF | 470 nF | 470,000 pF | Tone controls |
| 0.33 μF | 330 nF | 330,000 pF | Cross-over networks |
| 0.22 μF | 220 nF | 220,000 pF | Snubber circuits |
| 0.15 μF | 150 nF | 150,000 pF | Motor starting |
| 0.1 μF | 100 nF | 100,000 pF | Ceramic bypass |
| 0.068 μF | 68 nF | 68,000 pF | High frequency bypass |
| 0.047 μF | 47 nF | 47,000 pF | Signal processing |
| 0.033 μF | 33 nF | 33,000 pF | Audio filters |
| 0.022 μF | 22 nF | 22,000 pF | RF coupling |
| 0.015 μF | 15 nF | 15,000 pF | Oscillator circuits |
| 0.01 μF | 10 nF | 10,000 pF | Ceramic disc |
| 0.0068 μF | 6.8 nF | 6,800 pF | VHF circuits |
| 0.0047 μF | 4.7 nF | 4,700 pF | Tuning circuits |
| 0.0033 μF | 3.3 nF | 3,300 pF | RF bypass |
| 0.0022 μF | 2.2 nF | 2,200 pF | High frequency |
| 0.0015 μF | 1.5 nF | 1,500 pF | Crystal oscillators |
| 0.001 μF | 1 nF | 1,000 pF | HF applications |
| - | 0.68 nF | 680 pF | RF tuning |
| - | 0.47 nF | 470 pF | Variable tuning |
| - | 0.33 nF | 330 pF | Trimmer capacitors |
| - | 0.22 nF | 220 pF | Antenna tuning |
| - | 0.15 nF | 150 pF | VHF/UHF circuits |
| - | 0.1 nF | 100 pF | High Q circuits |
| - | 0.068 nF | 68 pF | Microwave circuits |
| - | 0.047 nF | 47 pF | Ultra high frequency |
| - | 0.033 nF | 33 pF | Precision timing |
| - | 0.022 nF | 22 pF | Clock circuits |
| - | 0.015 nF | 15 pF | Crystal references |
| - | 0.01 nF | 10 pF | Very high frequency |
0.1 μF = 100 nF = 100,000 pF
10 nF = 0.01 μF = 10,000 pF
1000 pF = 1 nF = 0.001 μF
47 μF = 47,000 nF = 47,000,000 pF
Capacitance is a measure of a capacitor's ability to store an electric charge. The SI unit of capacitance is the farad (F), named after the English physicist Michael Faraday.
A capacitor with a capacitance of one farad can store one coulomb of charge when a potential difference of one volt is applied across its terminals: C = Q/V.
In practical electronic circuits, capacitors typically range from picofarads (pF) to microfarads (μF), with specialized applications using larger values.
Capacitance values also sort neatly by role:
One quirk worth knowing: capacitor codes are written in picofarads, so 104 means 100,000 pF, which is 0.1 µF. And because Class 2 ceramics lose capacitance under DC bias and with temperature, the printed value is a nominal figure rather than what the part delivers in circuit — often by a wide margin.
| Prefix | Symbol | Factor |
|---|---|---|
| pico | p | 10−12 |
| nano | n | 10−9 |
| micro | µ | 10−6 |
| milli | m | 10−3 |
| kilo | k | 103 |
| mega | M | 106 |
| giga | G | 109 |
Two conventions cause real errors. Case matters: m is milli and M is mega, a factor of a billion apart, so writing mW when MW is meant is not a typo anyone can shrug off. And µ is frequently written as u because it is easier to type — 10uF and 10µF mean the same thing, and the substitution is universal enough in datasheets and schematics to be treated as standard.
Engineering notation — exponents restricted to multiples of three — exists precisely so that every value maps onto a prefix. It is why components are specified as 4.7 kΩ rather than 0.0047 MΩ, and why keeping values in that form makes mental arithmetic and cross-checking far easier.
Because picofarads keep the coded values as whole numbers. A code of 104 means 10 followed by four zeros in picofarads, which is 100,000 pF or 0.1 µF.
Often not. Class 2 ceramics lose substantial capacitance under DC bias and across temperature, so a 10 µF part may provide only a few microfarads at its working voltage. Check the manufacturer's bias curve.
m is milli, meaning one thousandth, and M is mega, meaning one million. They differ by a factor of a billion, so case must be written carefully.
Because µ is awkward to type on many keyboards and did not survive older character encodings. Writing 10uF for 10µF is standard practice in datasheets and schematics.
Scientific notation restricted to exponents that are multiples of three, so that every value corresponds to an SI prefix. It is why components are quoted as 4.7 kΩ rather than 0.0047 MΩ.