US Survey Acres to Hectares (ac (US) to ha)

1 US survey acre equals 0.404687261 hectares (rounded).

1 US survey acre = 0.404687261 hectares

How to convert US survey acres to hectares

To convert US survey acres to hectares, multiply the number of US survey acres by 0.404687261. The factor is rounded to 10 significant digits. To go the other way, multiply hectares by 2.47104393 (rounded).

hectares = US survey acres × 0.404687261

Example: 10 US survey acres = 4.04687261 hectares.

About these units

US Survey Acre (ac (US))

US land surveyHistorical unit (no longer in standard use)

43,560 square US survey feet (about 4,046.873 m²), slightly larger than the international acre. Used in US land records until 2022.

Two acres existed side by side in the United States for decades, separated by a tiny difference in the definition of the foot. Both contain 43,560 square feet, but the international acre uses the foot fixed in 1959 from a yard of exactly 0.9144 meter, giving 4,046.8564224 square meters. The survey acre keeps the older relation set by the 1893 Mendenhall Order, in which one meter is exactly 39.37 inches, giving about 4,046.873 square meters.

The gap is only about 0.016 square meter, roughly 160 square centimeters, but across a large state it adds up to real discrepancies, which is why surveyors held on to the old figure for land records. In October 2019 the National Geodetic Survey and NIST announced that the temporary continued use of the survey foot, mile and acre would end at the close of 2022, and the international units are meant to replace them. The acre itself began as the land a farmer with oxen could plough in a day, and its name comes from an Old Norse word for cultivated land.

1 US survey acre = 4,046.87261 square meters (approximately).

Sources: Wikipedia: Acre; NIST SP 811 Appendix B.8 (conversion factors)

Hectare (ha)

Metric (SI)Current unit

10,000 square meters (2.471 acres). The standard unit for land and agricultural areas outside the US.

Hecto plus are: the name was coined in French, and are itself comes from the Latin area, meaning an open space. The French law of 18 Germinal, Year III (7 April 1795) defined the are as 100 square meters, and the hectare followed as 100 ares, or 10,000 square meters. The unit is therefore a product of the original French metric reforms rather than of later SI work, which is one reason its official status has always been slightly awkward.

When the SI was set up in 1960 the are was not recognized, and the hectare was classed as a non-SI unit accepted for use with it. In practice it is the standard unit for land ownership, planning and agriculture in the European Union, the United Kingdom, Canada, Australia, New Zealand and South Africa, while the United States and Myanmar stay with the acre. A hectare is a square 100 meters on each side, about the size of Trafalgar Square, and equals roughly 2.47 acres. One hundred of them make a square kilometer.

1 hectare = 10,000 square meters (exactly).

Sources: Wikipedia: Hectare; Wikipedia: Are (unit); NIST Guide to the SI, Appendix B.8: conversion factors

Related conversions

See all area units.