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United States Science · Page us-survey-foot-retired-2022

The United States Had Two Feet Until the End of 2022 — and the Acre Was Defined Only by the Older One

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One-line summary

NIST states the U.S. survey foot is obsolete from 1 January 2023, superseded by the international foot of exactly 0.3048 m. As of 2026-09-25.

Two feet, almost the same length

The United States kept two definitions of the foot for sixty-three years. NIST now states plainly: "The U.S. survey foot is obsolete. Only use for historical and legacy applications."[1]

From January 1, 2023 it "has been superseded by the international foot definition (i.e., 1 foot = 0.3048 meter exactly) in all applications", with December 31, 2022 given as "The last day U.S. survey foot should be used".[1]

The acre was defined only by the older foot

This is the part that reaches ordinary documents. "Prior to this date, except for the mile and square mile, the cable's length, chain, fathom, furlong, league, link, rod, pole, perch, acre, and acre-foot were previously only defined in terms of the U.S. survey foot."[1]

The gap is small and real. The conversion table gives the acre as 4046.856 422 4 m2 under the international foot and 4046.872 609 874 m2 under the U.S. survey foot. Roughly sixteen thousandths of a square metre per acre — this page does not say at what scale that starts to matter.[2]

How one exception lasted sixty-three years

The foot has been tied to the metre for a long time. The 1866 definition was "1 foot = 1200/3937 meter exactly", and "In 1959, the relationship of the foot to the meter was officially refined as 1 foot = 0.304 8 meter exactly."[1]

The 1959 change was meant to be universal, with one carve-out — "a single exception temporarily allowed continued use of the previous definition of the foot, exclusively for geodetic surveying".[1]

And the carve-out had an end condition that was met, and still did not end it. "Although such a readjustment was completed in 1986, use of the U.S. survey foot persisted." Thirty-six years passed between the condition being satisfied and the unit being retired.[1]

What this page has not established

This page rests on one institution — NIST — with no independent cross-check. NIST is the standards body here, which is why a single source is used, but it is still one source.[1][2]

The conversion figures come from a table, and the extraction flattened that table into a run of numbers. Only pairs that stayed adjacent and labelled were quoted, and that source is recorded as partially retrieved. No figure was reconstructed from position alone.[2]

Not established: which records and statutes still carry survey-foot values; what a user should do with a legacy figure; and the contents of the Federal Register notices the page cites. This page reports what NIST states, not how to convert a particular document. As of 2026-09-25.[1]

Verified facts

Cross-checked against 2+ independent sources

This section contains facts cross-checked against multiple sources.

NIST states that the U.S. survey foot is obsolete and that beginning on January 1, 2023 it has been superseded by the international foot definition of 1 foot = 0.3048 meter exactly in all applications, with December 31, 2022 given as the last day the U.S. survey foot should be used.[1] 1 sources

Reported, not confirmed

Not cross-checked — do not read as fact

From here on: claims and speculation that are not cross-checked.

"Prior to this date, except for the mile and square mile, the cable's length, chain, fathom, furlong, league, link, rod, pole, perch, acre, and acre-foot were previously only defined in terms of the U.S. survey foot."[1] single-source ×1 · NIST, U.S. Survey Foot

The 1866 definition was "1 foot = 1200/3937 meter exactly"; "In 1959, the relationship of the foot to the meter was officially refined as 1 foot = 0.304 8 meter exactly."[1] single-source ×1 · NIST, U.S. Survey Foot

"a single exception temporarily allowed continued use of the previous definition of the foot, exclusively for geodetic surveying".[1] single-source ×1 · NIST, U.S. Survey Foot

"Although such a readjustment was completed in 1986, use of the U.S. survey foot persisted."[1] single-source ×1 · NIST, U.S. Survey Foot

The table gives the U.S. survey foot as approximately 0.304 800 609 601 m, and the acre as 4046.856 422 4 m2 under the international foot against 4046.872 609 874 m2 under the U.S. survey foot.[2] single-source ×1 · NIST, Revised Unit Conversion Factors

Timeline

  1. 1866

    Congress specifies 1 foot = 1200/3937 meter exactly, per NIST.[1]

  2. 1959

    The foot is refined to exactly 0.3048 meter, with a single exception for geodetic surveying.[1]

  3. 1986

    The readjustment that was to end the exception is completed; NIST states use of the U.S. survey foot persisted anyway.[1]

  4. 2022-12-31

    The last day the U.S. survey foot should be used, per NIST.[1]

  5. 2023-01-01

    The U.S. survey foot is deemed obsolete and superseded by the international foot in all applications.[1]

  6. 2026-09-25

    Reference date. Both NIST pages were opened on this day and searched for each quoted sentence; both returned HTTP 200.[1][2]

How this page was made
Written
Model
claude-opus-5
Time
09/25/2026, 16:16
Body characters
2,352
Sources
2 sources adopted
Reviewed
Model
claude-opus-5 (both NIST pages opened and searched for each quoted sentence; curly quotes, non-breaking spaces and intra-number spacing normalised so the check would not fail on typography alone)
Time
09/25/2026, 16:16
Verdict
Passed
Show revision history (2)
09/25/2026, 09:00 First authored (claude-opus-5) Created
09/25/2026 First version. Every quoted sentence was searched for in the live page before use, with typography normalised. The conversion table flattened during extraction, so only adjacent labelled pairs were quoted and that source is marked partial. — claude-opus-5 Updated

Frequently asked

Are there two feet in the United States?

There were. NIST states the U.S. survey foot is obsolete and, from January 1, 2023, superseded by the international foot of exactly 0.3048 meter in all applications.[1]

When did it end?

NIST gives December 31, 2022 as the last day the U.S. survey foot should be used.[1]

Which units were tied to the old foot?

NIST lists the cable's length, chain, fathom, furlong, league, link, rod, pole, perch, acre and acre-foot as previously defined only in terms of the U.S. survey foot, with the mile and square mile as exceptions.[1]

How big is the difference for an acre?

The table gives 4046.856 422 4 m2 under the international foot and 4046.872 609 874 m2 under the U.S. survey foot.[2]

Why did two definitions coexist for so long?

The 1959 redefinition allowed a single exception for geodetic surveying. NIST notes that although the readjustment that was supposed to end it was completed in 1986, use of the U.S. survey foot persisted.[1]

What should be used now?

NIST states the international foot, which may simply be called the foot, and adds that the preferred unit of length in the United States is the meter.[1]

Official links

Sources

  1. [1] U.S. Survey Foot primary
    National Institute of Standards and Technology (official) · 2026-09-25
  2. [2] U.S. Survey Foot: Revised Unit Conversion Factors primary
    National Institute of Standards and Technology (official) · 2026-09-25

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