How to Read Capacitors

Capacitance Values – and How to Read Them

Capacitors are used in a wide range of electronic components and circuits. They form an integral part of electronics. The capacitance of capacitors is measured in a unit known as Farads, represented by the letter ‘F’. A capacitor that has higher capacitance can be used for storing more charge as compared to one with a smaller capacitance value.

One Farad is a very high value for capacitance and usually smaller units are used, namely pico farad, nano farad etc. And as the capacitors are physically very small in size, their capacitance needs to be identified with a code mentioned on the capacitor itself. The exception to this is electrolytic capacitors that are big enough to have the capacitance value written directly on them.

Ceramic and film capacitors usually have a coded value marked on them. If the value marked on them is a two-digit whole number, then the capacitance is equal to the value mentioned in pico Farads. Thus a code of “10” implies that the capacitance is equal to 10 pico farads.

A three-digit whole number includes the first two significant digits, and the third digit as the multiplier (indicating the number of zeroes), and gives the value in pico Farads. Thus a code of “104” means, 10 multiplied by 10,000, giving the capacitance as 100,000 pF or 0.1 uF.

If a decimal number is used as the code on the capacitor, then the capacitance is equal to value mentioned in micro Farads. For instance, “.1” mentioned on the capacitor would imply 0.1 uF.

Finally, a whole number followed by the alphabet ‘n’ means the capacitance is equal to value mentioned in nano Farads.

In addition to the capacitance, the code on these electronic components can also be used for indicating the tolerance, voltage, and temperature properties.

470pF 3000V Capacitor

In the example above, the capacitor reads:

471M

3KV

The 471 is deciphered as 470pF; M=20% tolerance; 3KV=3,000V

Here are the codes for tolerance: