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In the schematics at the end of this document, there are a bunch of resistors. The author says in a footnote:

Part Notes, All Pages: Unless noted:
Resistors are 5%, 0.12 W, or better, for standard 5% values.
Resistors are 1%, 0.25 W, or better, metal film, for standard 1% values.
Resistors are 0.1%, 0.25 W, or better, metal film, if 4 significant digits are given.

But how do I know which resistors are 5%, 1%? The 0.1% is clear.

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This would likely be based on the E-series of preferred numbers. 5% values will be those from the E24 values, while 1% values will be those from the E96 values (shown in the list).

If you examine the values in the lists, you'll note that 5% values have only two significant digits while 1% values have three.

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  • \$\begingroup\$ So for example in the schematics, when I see R=1M it would be 5%, when I see 26.3K it would be 1%, when I see 10.00K it would be 0.1% and when I see 1.000k it would also be 0.1%, would you agree ? I am confused as to what people call significant digits here.. \$\endgroup\$
    – DarkBulle
    Commented Sep 25, 2023 at 15:26
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    \$\begingroup\$ I can't know the exact intention behind the schematic author, but I would surmise that if the author wrote "1.000k" instead of "1.0k" they intentionally did so to convey the precision without adding another line of text. The extra zeroes are meant to place the component into its precision category per the instructions. I agree that 10.00 and 1.000 are both 0.1%. One thing I would add: unless you are very cost-constrained, I wouldn't worry about or use 5% resistors. Use all 1% except where greater precision is needed, because the cost difference typically is negligible. \$\endgroup\$
    – JYelton
    Commented Sep 25, 2023 at 15:43
  • \$\begingroup\$ The schematics seem to be pretty clear - any of the values that are E96 only, are 1% tolerance. Any values that are ambiguous (like 100k) have a 5% next to them \$\endgroup\$
    – BeB00
    Commented Sep 26, 2023 at 2:09

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