I was taught the importance of this in my first year of Physics undergrad. Fermi approximations (or order of magnitude estimation), from Fermi problems (<a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Fermi_problem" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Fermi_problem</a>).<p>It is a highly valuable skill in STEM fields in my opinion. Sometimes knowing a rough number can tell you what to expect, and can immediately indicate whether something is wrong (or could go wrong).