Do reviewers go over the calculations (i.e do the calculations themselves) when reviewing? The question is clear:

Do reviewers go over the calculations (i.e do the calculations themselves) in the paper? For example, it can be the derivation of an equation, or some numerical calculations.

Edit:

What I am trying to understand is that if I am reading a paper and seeing some derivations, should I assume that someone (possibly reviewers) other than the authors went through those derivations in detail.

Edit 2:

The question can be narrowed down to STEM fields only.
This depends on the field, the paper, and the reviewer. If the result of a calculation seems to be "expected" by an experienced reviewer they may feel no need to go over the calculation in detail. An exception would be when it is a core result on which other things depend. Another exception is if the result surprises them in any way. 

And of course, some reviewers are much more meticulous than others and some fields require a lot of care because things can get subtle. 

But the author should, on the one hand, assume that they do, so that they don't get caught in error during review, but also assume that they don't so that they don't get caught in error later. (Confusing, I know). 

Ultimately it is the responsibility of the author to be correct and accurate and some errors do slip through review and don't get caught for a long time, if ever. People (authors and reviewers) do make mistakes, of course, but the combination of care from both tends to catch most errors.