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It's essential to be able to read '''capacitor codes''' in order to correctly recognise the correct part and as the schematic, BOM and component supplier might use pF, nF or µF interchangeably to be able to [[capacitor conversions|convert]] between these.
As small general purpose capacitors values range from a few pF to less than 1 µF the convention arose that whole numbers designate values in picofarads while decimal fractions designates values in microfarads. Any capacitor with a value of 1 µF or above is large enough to be marked with its actual value. A newer way to mark values is with three numbers on the body of the capacitor with the value in picofarads. The first two digits are the significant figures and the third the multiplier (i.e. number of zeros). So for example 151 indicates a capacitance of 150 pF.<ref>[https://web.archive.org/web/20120814104332/http://www.play-hookey.com:80/dc_theory/capacitor_values.html Reading Capacitance Values] by Ken Bigelow</ref>▼
== EIA scheme ==
The Electronic Industry Alliance (EIA) has standardised some of the marking schemes.<ref name="ccam"/>
== Leaded ==
On larger capacitors their value is printed on the case or encapsulation. The values of small capacitors are indicated in an alphanumeric code. With older capacitor values were sometimes indicated by a colour code.<ref name="ccam">[https://www.electronics-notes.com/articles/electronic_components/capacitors/capacitor-codes-markings.php Capacitor Codes & Markings], Electronics Notes</ref>
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Often p, n and u are substituted for the decimal point. For example 8p2 for 8.2pF, n51 for 0.51nF or 4u7 for 4.7µF.
=== Working voltage ===
Where there is space the working voltage is given. For smaller capacitors this needs to be found from the data sheet.<ref name="rcv"/>
=== Polarity ===
Care must be taken to insert polarised capacitors in the correct orientation. The stripe on radial or arrow on axial aluminium electrolytic types indicates the negative lead. On tantalum types a + sign indicates the positive lead.<ref name="rcv"/>
=== Stripe ===
If there is a stripe on a non-polarised capacitor, it might indicate which lead is connected to the outermost foil. To connect the capacitor connect this lead to the lowest impedance (usually the ground) side of the circuit. Many modern capacitors are unmarked, and often when a capacitor does have a stripe, it’s not related to the outside foil marking.<ref>[https://www.nutsvolts.com/magazine/article/finding-the-outside-foil-lead Finding the outside foil lead] by Chris Prioli, Nuts and Volts, Issue 2, 2022, p. 12</ref><ref>[https://e2e.ti.com/blogs_/archives/b/thesignal/posts/pcb-layout-tricks-striped-capacitors-and-more PCB Layout Tricks—striped capacitors and more] by Bruce Trump, The Signal, 11 Dec 2012</ref>
=== Small values ===
For small value capacitors the letter R is used to denote a decimal point.<ref name="ccam"/>
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=== Abbreviated marking codes ===
A newer way to mark values is with three numbers on the body of the capacitor with the value in picofarads. The first two digits are the significant figures and the third the multiplier (i.e. number of zeros). So for example 151 indicates a capacitance of 150 pF.<ref name="rcv"/>
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=== Temperature coefficient ===
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== SMD ==
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== References ==
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