This work was written as a supplementary text to help students understand the mathematical steps in deriving important equations in classical geophysics. It is not intended to be a primary textbook, nor is it intended to be an introduction to modern research in any of the topics it covers. It originated in a set of handouts, a kind of “do-it-yourself” manual, that accompanied a course I taught on theoretical geophysics. The lecture aids were necessary for two reasons. First, my lectures were given in German and there were no comprehensive up-to-date texts in the language; the recommended texts were in English, so the students frequently needed clarification. Secondly, it was often necessary to explain classical theory in more detail than one finds in a multi-topic advanced textbook. To keep such a book as succinct as possible, the intermediate steps in the mathematical derivation of a formula must often be omitted. Sometimes the unassisted student cannot fill in the missing steps without individual tutorial assistance, which is usually in short supply at most universities, especially at large institutions. To help my students in these situations, the “do-it-yourself” text that accompanied my lectures explained missing details in the derivations. This is the background against which I prepared the present guide to geophysical equations, in the hope that it might be helpful to other students at this level of study.