US Survey Foot vs International Foot: The 2022 NGS Deprecation
On October 1, 2022, the National Geodetic Survey (NGS) and NIST officially deprecated the US survey foot. All new federal surveys now use the international foot. The difference is 2 parts per million - but for land descriptions written before 2022, it still matters.
Updated April 2026
The Two Definitions Side by Side
International foot (current standard)
0.3048 m
Exactly 0.3048 metres. Defined by the 1959 International Yard and Pound Agreement. Used in all modern US, UK, and international measurements since 1959.
US survey foot (deprecated Oct 2022)
1200/3937 m
Approximately 0.30480060960 m. Based on the 1893 Mendenhall Order. Used for US federal land surveys from 1893 until October 1, 2022.
The difference
About 2 parts per million (2 ppm) - or approximately 1/8 inch over one mile. Over a single residential lot, this is sub-millimetre and unmeasurable in practice. Over a 10,000-acre ranch, it amounts to about 50 square feet.
Why Two Feet Coexisted for 63 Years
Before 1959, the United States defined the foot through the 1893 Mendenhall Order as exactly 1200/3937 metres. This gave the US survey foot its value of approximately 0.30480060960 m.
In 1959, the United States and five other English-speaking nations signed the International Yard and Pound Agreement, fixing the international yard at exactly 0.9144 metres and the international foot at exactly 0.3048 metres. This was cleaner, simpler, and aligned with the metric system.
However, the US retained the old survey foot specifically for land-survey and geodetic work to avoid the enormous administrative burden of reissuing decades of legal descriptions that relied on the old unit. So from 1959 to 2022, both feet coexisted: the international foot for most engineering and commercial use; the survey foot for federal land records, state plane coordinate systems, and geodetic datums.
The NGS announced the deprecation on September 14, 2022, effective October 1, 2022. All new federal surveys, NOAA charts, geodetic measurements, and state plane coordinate system updates now use the international foot.
Practical Impact on Acres and Property
| Scale | Intl acre (sq ft) | Survey acre (sq ft) |
|---|---|---|
| 1 acre | 43,560.000 | 43,560.174 |
| 160 acres (quarter section) | 6,969,600.0 | 6,969,627.9 |
| 640 acres (section) | 27,878,400.0 | 27,878,511.5 |
| 10,000 acres | 435,600,000 | 435,601,742 |
For a typical residential lot (under 1 acre), the difference is less than 0.2 sq ft - unmeasurable in practice. The difference only becomes meaningful at very large land scales (10,000+ acres) and even then is rarely legally significant.
Who This Affects
Surveyors writing new legal descriptions
Use the international foot for all new work. State plane coordinate systems have been updated (SPCS 2022) to the international foot.
Title researchers reading old deeds
For pre-2022 federal land records (BLM plats, state-land grants referencing federal surveys), assume the survey foot was used unless the document specifies otherwise. The practical difference is sub-0.001% for most parcels.
GIS professionals
Update workflows and transformations to SPCS 2022 (international foot). Legacy data sets using the old state plane definitions may show small coordinate shifts of a few centimetres in some states.
Average homeowner
No practical impact. Your property boundaries did not move. No resurvey is needed.
International buyers
Both feet are already well within the precision of GPS parcel measurement. This change has no practical effect on international real estate transactions.