Capacitor Value Reference

The first two digits of a capacitor value reference give you a number that you then divide or multiply by factors of ten according to the value of the third digit.

Marking	Value (in microfarads – µF – unless otherwise stated)
Nn	Picofarads (nn is a number from 01 to 99)
101	100 pF
102	0.001
103	0.01
104	0.1
221	220 pF
222	0.0022
223	0.022
224	0.22
331	330 pF
332	0.0033
333	0.033
334	0.33
471	470 pF
472	0.0047
473	0.047
474	0.47

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Source:http://www.dummies.com/how-to/content/capacitor-value-reference.html