The plural of the word ‘formula’ is ‘formulas’ or ‘formulae’. Both forms are correct, but their usage can vary based on the context.
‘Formulas’ is the more common plural in everyday English, especially in casual settings and in American English. For example, you might say, ‘The scientist tested several different formulas to find the best solution.’
On the other hand, ‘formulae’ is used more frequently in formal contexts, particularly in scientific or mathematical writing. For instance, one might write, ‘The physicist presented several key formulae in her paper.’
In summary, you can use either ‘formulas’ or ‘formulae’ depending on the tone and context of your writing.