Most capacitors will have their value printed on them.
However there are a number of capacitors manufacturers who use the 'IEC'
code. the 'IEC' code is a numerical code that works in a similar way to
the resistor colour code: two figures followed by a multiplier.
Quite often there is a single letter, indicating tolerance.
The code is worked out in picofarads, so there is a chance you may have to use the appropriate multiplier. For example a capacitor may have a code '104k'. This decodes as OluF 10%. The first two figures give 10 the third figure'4' gives 0000 and the last 'k' = 10%. Therefore, the capacitor is 10,0000pF, 10%. This is normally expressed as 0.0luF or l00nF - capacitors with a value below 0.001uF are expressed in Picofarads.
There may be a further figure marked on the capacitor, this would normally be the maximum voltage rating.
1st figure of value |
2nd figure of value |
Number of Zeros (multiplier) |
Tolerance (+/-%) |
pF
nF
uF
mF
EIA Code
100
0.1
0.0001
-
l0l
820
0.82
0.00082
-
821
1000
1
0.001
-
102
8200
8.2
0.0082
-
822
10,000
10
0.01
-
103
82,000
82
0.082
-
823
100,000
100
0.1
0.0001
104
-
820
0.82
0.00082
824
-
1,000
1
0.001
105
-
8,200
8.2
0.0082
825
-
10,000
10
0.01
106
-
82,000
82
0.082
826
-
100,000
100
0.1
107
-
-
820
0.82
827
-
-
1000
1
108
-
-
8200
82
828
-
-
10,000
10
109
-
-
82,000
82
829
-
-
100,000
100
-
-
-
-
820
-
-
-
-
1000
-
Usually capacitors are marked with the 'V' symbol.
Most electrolytics clearly indicate their voltage rating polyester or greencaps usually show the voltage - less the 'V' symbol. Quite often ceramics show no voltage ratings at all.
Tolerance indicates how close the capacitors marked value is to its actual value A tolerance can be marked several ways, numerically, as a code. Consisting of a single letter or a colour band or dot. Tolerance code letters are usually placed immediately after the value. Commonly used tolerance codes are:
Code | Colour | Tol. | Code | Colour | Tol. |
A | - | +20-10(z) | L | - | +/-15% |
C | Red | +/-0.25pf | M | Black | +/-20% |
D | Green | +/-0.5pf | N | - | + /-30% |
E | White | +/-1pf | P | - | + 100 -0 |
F | Brown | +/-1% | Q(2) | - | +30-10 |
G | Red | +/-2% | S | - | +50-20 |
J | Green | +/-5% | W | - | +50-10 |
White | +/-IO% | W(2) | - | +40-20 | |
Z | Grey | +80-20 |