order of magnitude

order of magnitude (plural orders of magnitude)

1. The class of scale or magnitude of any amount, where each class contains values of a fixed ratio (most often 10) to the class preceding it. For example, something that is 2 orders of magnitude larger is 100 times larger, something that is 3 orders of magnitude larger is 1000 times larger, and something that is 6 orders of magnitude larger is a million times larger, because ${\displaystyle 10^{2}}$ = 100, ${\displaystyle 10^{3}}$ = 1000, and ${\displaystyle 10^{6}}$ = a million.
   • 2011, Enrico Fermi, Wikisource (translator), Concerning a Contradiction between the Electrodynamic and Relativistic Theory of Electromagnetic Mass, 1922, Enrico Fermi, Über einen Widerspruch zwischen der elektrodynamischen und relativistischen Theorie der elektromagnetischen Masse, Physikalische Zeitschrift, v 23, pp 340-344,

     However, we notice that although this contraction is of order of magnitude ${\displaystyle v^{2}:c^{2}}$ , it changes the most important terms of electromagnetic mass, i.e, the rest mass.

• dex
• ballpark figure (colloquial)