A capacitor code generally consists of three numbers. The first number, reading from the left, is called the first significant figure. The second number is called the second significant figure. The third number is the multiplier and that number corresponds to the number of zeros to be added after the first and second significant figures to get the capacitance of the device, in farads. For example, a capacitor with the code 142K would have a capacitance of 1.4 nF and a tolerance of +/- 10%. A capacitor with a 25-microfarad capacitance and +/- 20% tolerance would have a code of 256M.
Following the number is a letter. The letter describes the tolerance of the device in a percentage value.
In cases where color bands are also used, extra bands indicate the temperature coefficient and the voltage rating class of the device. On capacitors where a black band is present, it indicates the end of the capacitor that is intended to be hooked up to the chassis ground.