# Adding a caption to an equation in org-mode

I'd like to add a caption to a LaTeX-formatted equation, using org-mode's build-in #+caption: directive. The manual says this is possible, but does not specify exactly how to format it. The most intuitive methods do not work; I tried all of the following:

#+caption: Kepler's third law
[\ T^2 = \frac{4\pi^2}{G(M_1+M_2)} \]

#+caption: Kepler's third law
#+latex: $T^2 = \frac{4\pi^2}{G(M_1+M_2)}$

#+caption: Kepler's third law
$$T^2 = \frac{4\pi^2}{G(M_1+M_2)}$$


All three of these formattings result in the equation being rendered, but not the caption. I know it is possible to insert captions directly using LaTeX, but I would like to use the org native method, which the manual says I can do. How can I do it?

• Why do you want such a behaviour? It looks quite strange to me. However, assuming you want to succeed with that solution, I'd change equation to equation* to avoid showing the equation number. – exilsteira Nov 19 '20 at 8:25
• @exilsteira The document I'm writing warrants captioned, enumerated equations, and I prefer doing things natively in org when possible rather than hand-writing latex code. – slondr Nov 21 '20 at 4:26

I managed to guess-and-check my way to finding an answer to this!

The trick is to wrap the equation in a figure:

#+caption: Kepler's third law
#+begin_figure
$$T^2 = \frac{4\pi^2}{G(M_1+M_2)} R^3$$
#+end_figure


This applied the caption correctly.

For posterity's sake, if you want to pass position options to the figure using this method, you need to use :options [] instead of :placement []. I have no idea why, though.