Yes it is, the same way that vertices is the plural of vertex, matrices is the plural of matrix, bacteria is the plural of bacterium, data is the plural of datum, and media is the plural of medium.
Please you make sure that you are aware of this fact.

Don't make me tell you this more than once.

"Formulas", of course, is also a perfectly acceptable plural form of formula". Ask Merriam-Webster. Or Webster 1913, for that matter. "Vertexes" is also an acceptable plural form of vertex.

The Latin plural would most certainly be formulae. However, we don't speak Latin, we speak English. So, the choice of plural is left to the speaker at hand, whether one wants to stick with the Latin origins or comply with standard English plurals. Neither of them is wrong, English does not have some large official institution dictating its exact form, as far as I know.