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What is the difference between a 1206, 0805 and a 0603 SMD resistor, as far I know they all have a resistance of 10.7K?

I going to need one for my little 5v DC buck converter.

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    \$\begingroup\$ Size. And voltage rating. \$\endgroup\$ May 21, 2018 at 22:52
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    \$\begingroup\$ Actually, all of them don't have a resistance of 10k7. A very small percentage of them do. \$\endgroup\$
    – Wesley Lee
    May 22, 2018 at 3:26
  • \$\begingroup\$ @WesleyLee Thank you, for your answer. Didn't know they were size codes, before now. Thanks for clearing it up. \$\endgroup\$
    – Artonn
    May 22, 2018 at 14:00

3 Answers 3

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The codes you are referring to are size codes, e.g. 1206 means 0.125x0.060 inches.

There are some other differences, except for size.

Smaller resistors probably feature a lower power and voltage rating, but can have smaller parasitic components, ESL and parallel capacitance. I would not expect the parasitics to be an issue, just be sure to get one with the required power rating.

If you need to hand solder them, I suggest not going too small,e specially if you do not have any experience. 0603 should be fine for almost everyone, 0805 even more so, 1206 is a huge beast you can solder with your hands tied and your eyes closed.

As usual, if you have doubts always refer to the manufacturer datasheet.

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  • \$\begingroup\$ Thank you very much for your explanation, I'm very new to this but I find it very interesting. I'll go with the 0603 as I believe they're close to the size used on this one: i.imgur.com/lu5EzTr.png \$\endgroup\$
    – Artonn
    May 22, 2018 at 13:56
  • \$\begingroup\$ those look more like 0805 or 1008 actually \$\endgroup\$ May 23, 2018 at 6:57
  • \$\begingroup\$ I found my digital ruler and measured them now, they're 0805 and 1206 sized. Now I just need to identify that damn chip. \$\endgroup\$
    – Artonn
    May 23, 2018 at 16:36
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    \$\begingroup\$ 1206 is clearly not a “huge beast” and a complete novice will not be able to “solder with your hands tied and your eyes closed”. For an experienced person it might seem that way but commentary like this is a real put off for those starting out \$\endgroup\$
    – Raoul
    Feb 14, 2023 at 21:59
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Here are the relative SMT sizes:

enter image description here Source: groups.io

Usually size also corresponds to power rating (the more surface area and pin area the part has, the more heat it can dissipate and the larger amount of power it can handle.

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They are different sizes.

1206 means 0.12 inches by 0.06 inches (3.2 x 1.6 mm). 0603 means 0.06 by 0.03 inches (1.6 by 0.8 mm). And so on. (Wikipedia)

The smaller ones will most likely have lower power and voltage ratings, because they are smaller.

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