Capacitor tolerance codes
As mentioned, that letter following the value (e.g., the "M" in "104M") is the tolerance of the cap. Since I have it handily stored here on the HDD, I'll just pop it onto this post for all to have handy. This list isn't found just anywhere and there are a few recently-added letters that I found that I hadn't known about. The non-symmetrical tolerances, e.g., +80/-20%, are used on "bulk" capacitors, those caps that are used for power supply filters and decoupling, where you want capactance, the more the merrier, but don't want it below a certain value. Here's the codes:
B = ±0.1pF
C = ± 0.25pF
D = ±0.5pF
E = ±0.25%
F = ±1.0pF
G = ±2%
H = ±2.5%
J = ±5%
K = ±10%
L = ±15%
M = ±20%
N = ±30%
P = -0, +100%
S = -20, +50%
W = -0, +200%
X = -20, +40%
Z = -20, +80%
Dean