Plural of Formula

The Quick Answer
The plural of formula is formulas or formulae.

The Plural of Formula

The plural of formula is formulas or formulae.
  • Formulas are applied to provide a mathematical solution for real world problems.
  • Formulae are used to express relationships between various quantities.
The noun formula has a Latin root, which is the derivation of the plural formulae. Through common usage, formulas (which adheres to the standard rules for forming plurals) is also now acceptable.

The table below shows the standard rules for forming the plurals of nouns in English.

Type Example of Type Forming the Plural Plural
Most Nouns formula
scythe
add s formulas
scythes
Noun Ending s, sh, ch, x or z box
dress
add es boxes
dresses
Nouns ending [consonant] o hero
zero
tomato
add either s or es
(There are no rules for this - you have to know.)
heroes
zeros
tomatoes
Nouns ending [vowel] o patio
ratio
add s patios
ratios
Nouns ending [consonant] y story
penny
change the y to an i and add es stories
pennies
Nouns ending [vowel] y donkey
chimney
add s donkeys
chimneys
Nouns ending f or fe dwarf
hoof
ves and/or s
(There are no rules - you have to know.)
dwarfs
hooves or hoofs
Exceptions man
louse
some nouns undergo a vowel or letters change men
lice
More exceptions salmon
sheep
some nouns do not change at all salmon
sheep
Foreign rulings formula
medium
some nouns adopt foreign rulings formulae
media

Why Is There Confusion over the Plural of Formula?

Confusion arises over the plural of formula because its original plural form (formulae) derives from Latin, and native English speakers are drawn to formulas, which adheres to the standard ruling for forming plurals.

Both formulae and formulas are acceptable, but formulas is the more common plural and the safest option. (See the evidence in Google's Ngram Viewer.)

See Also

Unusual pluralsPlural forming table Quirks with forming plurals Forming the plurals of abbreviations Forming the plurals of compound nouns