Plural of “foot”

The plural of foot is feet.

Why

Like "mouse/mice," "foot/feet" reflects the Old English i-mutation sound process: an old plural ending (now lost) pulled the vowel in "fot" forward, producing "fet," which regular sound changes later shaped into the modern "feet." This is a purely Germanic vowel-shift mechanism, unrelated to any Latin or Greek borrowing pattern.

"Foot" as a unit of measurement (12 inches) has its own separate plural convention: when used adjectivally before a noun, it stays singular ("a six-foot fence," not "a six-feet fence"), while as a standalone measurement it still pluralizes normally ("the fence is six feet tall") — a distinction that applies to several English measurement nouns (a ten-year-old, but she is ten years old). The idiom "put your foot down" (to act with sudden firmness) and "get off on the wrong foot" (to start badly) both stay locked in the singular no matter how many people are actually involved, treating "foot" here as a fixed idiomatic unit rather than a literally countable body part — the same freezing effect seen across many other body-part idioms, which lock in a particular grammatical number regardless of the real-world situation being described.

Usage note

The plural "feet" is used without exception for the body part and the standalone unit of measurement; the only real variation is the adjectival-vs-standalone distinction above, which trips up writers more often than the core foot/feet irregularity itself. "Footing," a related noun describing a stable position or basis ("lost his footing," "on equal footing"), is fully regular and uncountable, showing no trace of the body-part noun's irregular plural, since it derives from "foot" used as a verb-like base rather than as the countable body part itself.

The adjectival-singular convention ("a six-foot fence") extends to a whole class of English measurement nouns used before another noun — a ten-year-old, a five-pound weight, a two-hour delay — where the measurement noun stays singular specifically because it's functioning grammatically as an adjective, not as a counted noun in its own right. The United States remains one of the only major economies still using "feet" as an everyday unit in construction, real estate, and aviation altitude, while most of the English-speaking world converted to metric decades ago — a genuine ongoing linguistic and practical divide that keeps "foot/feet" far more current in American English than in British or Australian English, where the unit survives mostly in older buildings' recorded measurements and a handful of fixed idioms.

Common real mistakes

Writing "a six-feet fence" instead of the correct "a six-foot fence" is a common real error — when the measurement functions as an adjective directly before a noun, it stays in the singular form. A related, purely stylistic point: some American style guides recommend spelling out "foot" or "feet" in formal prose rather than using the symbol ′ (a single or double prime mark), reserving the symbol strictly for technical drawings, surveying documents, and real-estate listings where space is limited.

The wider pattern

The identical i-mutation vowel-shift mechanism, from the same period of Old English sound change, produced "tooth/teeth," "goose/geese," "mouse/mice," and "louse/lice" — recognizing this one pattern actually explains five of English's most common irregular plurals at once, rather than requiring five separate memorized exceptions.

Examples

• She had blisters on both feet after the hike.
• The fence is exactly six feet tall.
• He built a six-foot fence around the garden.
• Their feet were cold after walking in the snow.
• The dancers moved their feet in perfect rhythm.
• Ten feet of rope should be enough for the job.
• The trail climbs nearly a thousand feet in elevation.
• He measured the room at twelve feet by ten feet.
• Her feet ached after standing all day.
• The bridge spans about two hundred feet across the river.