Square Feet to US Survey Acres (ft² to ac (US))

1 square foot equals 0.00002295674931 US survey acres (rounded).

1 square foot = 0.00002295674931 US survey acres

How to convert square feet to US survey acres

To convert square feet to US survey acres, multiply the number of square feet by 0.00002295674931. The factor is rounded to 10 significant digits. To go the other way, multiply US survey acres by 43,560.17424 (rounded).

US survey acres = square feet × 0.00002295674931

Example: 10 square feet = 0.0002295674931 US survey acres.

About these units

Square Foot (ft²)

US & ImperialCurrent unit

Exactly 0.09290304 m². The standard unit for floor areas and real estate in the US, UK and India.

Feet came first, and they were not all the same length. As a body-based unit, the foot ranged historically between about 250 and 335 millimeters, with ancient Greek and Roman feet near 300 mm. In medieval England a statute foot was set at 10/11 of an older Belgic foot, and Charlemagne's attempt around 790 to standardize units largely failed. The square foot is simply that length squared, so its size changed along with the foot.

The 1959 international agreement fixed the foot at exactly 0.3048 meter, so one square foot is exactly 0.09290304 m², or 144 square inches. The United Kingdom adopted the new foot in 1964. Today the square foot is the usual way of listing property in the United States, Canada, the United Kingdom, India, Pakistan, Singapore and Hong Kong, although the measuring convention varies: agents may measure corner to corner, subtract unheated space, or add heated space that extends beyond the end-to-end measurement. The world's smallest park has been reported at 2.6 sq ft.

1 square foot = 0.09290304 square meters (exactly).

Sources: Wikipedia: Square foot; Wikipedia: Foot (unit); NIST Guide to the SI, Appendix B.8: conversion factors

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)

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