Plural of Formula
Both “formulas” and “formulae” are accepted plurals of “formula.” Do not present “formulae” as the only correct plural or treat “formulas” as an error: both are dictionary-recorded forms.
Both “formulas” and “formulae” are accepted plurals of “formula.”
Key details
Choose the right form
| Meaning / situation | Form / construction | Decision |
|---|---|---|
| one rule, expression, recipe, or fixed method | formula | Use the singular form. |
| regular English plural | formulas | Accepted plural. |
| Latin-derived plural | formulae | Also accepted. |
Quick tests
Meaning / construction test
Do you need the plural of “formula”?
If yes: Use either “formulas” or “formulae,” following field or house style and staying consistent.
If no: Use singular “formula” for one item.
Caveat: Both plural forms are standard; a technical field may prefer one, but the alternative is not automatically an error.
Examples
The handbook lists three formulas.
“Formulas” is an accepted regular English plural.
The appendix compares several formulae.
“Formulae” is an accepted Latin-derived plural.
This formula is easy to apply.
One item takes the singular “formula.”
Further guidance
Core difference
Both “formulas” and “formulae” are accepted plurals of “formula.”
Fast Test
Use the form expected by the field, publication, or house style; otherwise keep the choice consistent within a document.
Usage Boundary
Do not present “formulae” as the only correct plural or treat “formulas” as an error: both are dictionary-recorded forms.
Sources and evidence
Sources are shown with the role they play in this guide. Historical or style-sensitive claims are kept within the evidence boundary described above.
- Formula — Merriam-Webster (opens in a new tab)Merriam-Webster · Dictionary evidence recording both formulas and formulae as plurals of formula.