Acres to Hectares Converter

What an Acre and a Hectare Measure

An acre and a hectare both measure land area, and both are fixed numbers once you express them in square meters. An acre is 43,560 square feet exactly, which works out to 4,046.8564224 square meters. A hectare is 10,000 square meters exactly, as listed by the BIPM SI Brochure as a non-SI unit accepted for use with the SI.

Because the hectare is the bigger unit, the acre number comes out smaller: 1 acre = 0.40468564224 hectare. Flip it around and 1 hectare = 2.471053814671653 acres. A quick mental picture: two and a half acres fit inside one hectare, with a little room left over.

The National Institute of Standards and Technology keeps the official US tables of units, and those tables carry these area figures as exact values, not rounded estimates. That matters when a deed, a lease, or a crop report needs numbers that hold up to auditing.

The Exact Conversion and Where the Numbers Come From

The acre to hectare relationship is not a surveyor's approximation. It is exact, and it follows from one decision made in 1959. That year, the United States and the United Kingdom agreed on the international yard and pound: 1 yard = 0.9144 meter exactly. Since a foot is a third of a yard, 1 foot = 0.3048 meter exactly, and 1 square foot = 0.09290304 square meter exactly.

An acre is 43,560 square feet by definition, so multiply: 43,560 x 0.09290304 = 4,046.8564224 square meters. Divide by the hectare's 10,000 square meters and you get 1 acre = 0.40468564224 hectare, exact to the last digit. NIST Handbook 44, Appendix C (2024 edition) prints exactly this chain, with the underlined figures marked as exact.

For everyday work, most people round to 1 acre = 0.4047 hectare or 1 hectare = 2.471 acres. The error from that rounding is under 0.01 percent, which is far smaller than the tolerance on any property survey.

Quick Reference Conversion Table

The table below covers the sizes that come up most often in US land talk: the quarter acre lot, the 40 acre quarter quarter section, the 640 acre section, and the sizes in between. Hectare values are rounded to 4 decimal places; square feet and square meters carry their exact or near exact values.

Reading a few rows out loud helps the scale stick. A quarter acre homesite is about a tenth of a hectare. Ten acres is just over 4 hectares. A full square mile section of 640 acres is 259 hectares, which is why European farm reports written in hectares describe US ranches with much smaller looking numbers.

Convert by Hand: Two Worked Examples

Acres to hectares, step by step. Take 5 acres. Multiply by 0.40468564224: 5 x 0.40468564224 = 2.0234282112, so 5 acres = 2.0234 hectare after rounding to 4 places. If you also want square feet, multiply by 43,560 instead: 5 x 43,560 = 217,800 square feet.

Hectares to acres, step by step. Take 3 hectares. Multiply by 2.471053814671653: 3 x 2.471053814671653 = 7.413161444014959, so 3 hectares = 7.4132 acres. In square meters the same parcel is 30,000 m2, because a hectare is 10,000 m2 with no rounding involved.

A cross check catches most hand mistakes. Convert one way, then convert back with the other factor. Start with 10 acres, get 4.0468564224 hectare, then multiply that by 2.471053814671653. You should land back on 10 within calculator rounding. If the round trip misses by more than the last digit or two, a factor went in the wrong slot.

One more guard: keep the direction straight by remembering which number is bigger than 1. Hectares to acres multiplies by about 2.47 and grows the number. Acres to hectares multiplies by about 0.405 and shrinks it. If your result moved the wrong way, you swapped the factors.

The Full Unit Ladder Across Six Area Units

Land documents bounce between six area units, so it helps to see the whole ladder in one place. Every row below is exact where the digits allow it, taken from the NIST Handbook 44 area tables.

Two anchors make the table easy to rebuild from memory. First, 640 acres fill a square mile, so a square mile is 258.9988 hectare. Second, a square meter is a tenth of a percent of an are and a hectare holds 100 ares, so 1 m2 = 0.0001 ha without any conversion factor at all.

The square yard row explains an old land unit: an acre is 4,840 square yards, and that odd number comes from the historical definition of a furlong by a chain, 660 feet by 66 feet. Neither number is round in feet, but the product lands on 43,560 square feet.

Hectares and Acres in Real Life

Concrete objects make the two units feel different sizes. An American football field, 360 feet by 160 feet including the end zones, covers 57,600 square feet. That is 1.3223 acres, or 0.5351 hectare. So one hectare holds a football field with roughly a third of an acre of parking left over.

A FIFA regulation soccer pitch measures 105 m by 68 m, which is 7,140 m2. That is exactly 0.714 hectare by definition of the meter, and it converts to 1.7643 acres. A regulation NBA court, 94 by 50 feet, is 4,700 square feet, or 0.1079 acre, so it takes more than nine courts to fill one acre.

For the farm row, the USDA Census of Agriculture put the average US farm at 463 acres in 2022, which converts to about 187.4 hectares. European farm statistics quoted in hectares describe the same operation with a number less than half the acre figure, which is the whole reason the two units get confused across borders.

The US Survey Acre and the 2023 Switch

Between 1959 and the end of 2022, the United States ran two foot definitions at once. The international foot was 0.3048 m exactly. The US survey foot, kept for geodetic surveying, was 1,200/3,937 m, a hair longer. Each foot definition carried its own acre: the international acre at 4,046.8564224 m2 and the US survey acre at 4,046.872609874 m2.

The gap is about 4 parts per million, or 0.016187 m2 per acre. On a suburban lot nobody could ever detect it. On a 640 acre section it adds up to about 10.36 m2, roughly the footprint of a one car garage, and still only 0.0010 hectare.

That era is over. A Federal Register notice finalized in October 2020 set the retirement date, and the official deprecation notice states that from January 1, 2023 the US survey foot should not be used and the international foot is the only approved definition. NIST explains the transition on its U.S. Survey Foot page.

Older deeds and county GIS records recorded before 2023 may still quote survey foot based areas. Those remain valid history, but any new measurement or conversion should use the international figures in this page, which is what the calculator above does.

Common Mistakes When Converting Land Area

Square units do not behave like the lengths underneath them, and that trips up more conversions than any memorized factor. Doubling a side length quadruples the area. A lot that is 100 by 200 feet is 0.4591 acre; a lot that is 200 by 400 feet is four times that, 1.8365 acre, not double.

Mixing linear and square units is the second classic error. An acre is 43,560 square feet, but you cannot divide a perimeter by anything to get it. If someone offers an acreage figure from fence line length, redo the area from two perpendicular measurements instead.

Rounding too early is the third. Multiply 2.47 by 37 hectares and you get 91.39 acres; the exact product is 91.42899114285117 acres. On large parcels the sloppy factor drifts the answer by most of an acre, which matters in a purchase price. Keep the full constant, round once at the end.

Fourth, watch the decimal place on hectares to square meters. Because 1 ha = 10,000 m2, moving four places is the whole job. Writing 2.5 hectare as 2,500 m2 instead of 25,000 m2 is a tenfold error that no calculator above will make, but hand notes do it constantly.

Last, remember the calculator here and the exact constants come from NIST tables, and that a converted figure is a mathematical fact, not a legal description. For anything that binds a contract, the recorded plat and a licensed survey govern.