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As in normal ceramic and carbon film resistors we can calculate by color codes but nothing mention over the smd components so how to get it? As nothing is ideal so I believe there will be some tolerance level in it also.

please help :)

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  • \$\begingroup\$ MELF resistors do have color codes … \$\endgroup\$
    – CL.
    Jun 20 '17 at 17:25
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    \$\begingroup\$ The answer is: Read the datasheet. As with "normal" through-hole resistors there are many tolerance levels. There is no "standard" tolerance for SMD resistors. If you do not have a datasheet and you have no clue which model an SMD resistor is, you can only guess the tolerance. \$\endgroup\$ Jun 20 '17 at 17:29
  • \$\begingroup\$ @Bimpelrekkie is exactly correct, but I'm going to go out on a limb and say that the vast majority of SMT resistors out there are 1% tolerance. \$\endgroup\$
    – John D
    Jun 20 '17 at 17:33
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You can't tell without the datasheet, though there are some hints- usually precision resistors are thin film and look a bit different from thick film. Most consumer products use 5% resistors, some use 1% or better. There are similar size resistors that are 0.1% or even 0.01%, with commensurately better stability and stunningly high price tags (at the low end they are almost free, a reel of 10,000 costing less than a decent lunch, about the cost of a single high precision resistor).

You may be able to tell something from the resistance marking (if any, many smaller parts are not marked at all). If it's made to an E96 series value it's 1% or better, but it's also possible a 2.7K resistor could be 1% tolerance. If it is marked with the 3 character alphanumeric code it's 1% or better.

There are a lot of other things you don't know without a part number, manufacturer and datasheet/manual- the rated power dissipation, the maximum voltage, the temperature coefficient, the rated stability and so on. Tolerance is just one more unknown.

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Guessing would put you in a very vague realm. Just looking at a single online catalog and pulling up all of the SMD/SMT resistors that they carry, the tolerances range from 0.01% to 30%, some with differing values of + and - tolerances. The data sheet would be the only real way to know.

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