“Foot” and “feet” follow the same rule whether you’re describing a body part or a measurement: “foot” is singular, “feet” is plural, with one notable exception. When “foot” acts as part of a hyphenated compound adjective, the singular form stays even for large numbers.
Since 1959, one foot has been precisely defined as 0.3048 meters, making it a fixed unit in both the British imperial and United States customary systems. Read on to understand exactly when to use each form, why “foots” has never been correct, and how compound adjectives change the picture.
Meaning and Usage of Foot
Foot has a few predominant meanings:
A body part 👣 The foot is the body part at the bottom of the leg, typically with ten toes.
A measurement 📏 Foot is also a unit of length in the imperial system, equaling twelve inches, with three feet making one yard. Its division into 12 inches traces back to ancient Rome, where the unit was based on the length of a male foot. Since an international agreement in 1959, one foot equals exactly 0.3048 meters. When a number precedes the unit, “foot” can stand in for the plural, as in “that man is six foot tall.”
The bottom or end of something ⬇️ Because we think of human feet as being at the end of our bodies, this meaning extends to non-human things. “The foot of the mountain” is the base, and notes at the end of a page are called “footnotes.”
These are the most common uses. (As a Shakespearean aside: “foot” also refers to a group of syllables in poetry, but that’s a niche usage for another day.)
Difference Between Foot and Feet
Feet is the plural form of foot for both the body part and the unit of measurement. One foot, two feet. “Feet” is an irregular plural, formed by a vowel change rather than by adding “-s,” following the same pattern as “tooth/teeth” and “goose/geese.” That’s why “foots” has never been standard English.
Examples of Foot and Feet in a Sentence
When “foot” forms part of a hyphenated compound adjective modifying a noun, the singular form stays regardless of the number:
- a thirty-foot boat
- an eight-foot couch
- a hundred-foot building
- a six-foot ladder
The same logic applies to “a hundred-dollar watch” or “a four-layer cake”: the noun being modified does the work, and the measurement just describes it. So while we say “The pole is ten feet long,” we’d also say “a ten-foot pole.”
There is one additional exception: in informal spoken English, especially for describing a person’s height, “foot” is commonly used as a predicative singular even without a hyphen — “He is six foot tall.” This is widely accepted in British English and informal American English, though formal writing and style guides generally prefer “six feet tall.” The hyphenated form “six-foot-tall man” follows the compound adjective rule and is always correct.
Footnote: Why Don’t We Say Foots?
English has one dominant method of forming plurals: add “-s.” Old English, spoken about a thousand years ago, had several methods inherited from its Germanic roots, including vowel shifts (tooth/teeth) and different endings (child/children). As the language evolved, “-s” plurals took over, but a handful of words held their ground.
“Feet” is an instance of i-mutation, also called umlaut. In Proto-Germanic, the singular was fōt-s and the plural fōt-iz; the “i” vowel in the plural suffix caused the “ō” in the root to shift, eventually producing “feet” once the suffix itself disappeared. English retains seven of these “mutant plurals,” where the vowel changes rather than an “-s” being added: foot, woman, man, tooth, goose, mouse, and louse. Foot has held this irregular plural for over a thousand years, which is why “foots” has never been the correct form.
Conclusion
Different style guides offer specific guidance on how to handle feet and inches in writing:
- AP Style: Spell out feet and inches in most contexts; use figures for dimensions (a 5-foot-6 man).
- Chicago Style: Follow the same figure/word rules as AP for most measurements.
- Abbreviation: ft (no period in technical writing; ft. with a period in non-technical AP style).