How many hectares are in 1 acre?

1 acre equals 0.4046856422 hectares, using the exact defined conversion factor rather than an estimate.

How do I convert acre to hectare?

Multiply the acre value by 0.4046856422. The converter above does this instantly to whatever precision you set.

How do I convert hectare back to acre?

Use the reverse factor: 1 hectare equals 2.471053815 acres. You can also use the swap control in the converter above to flip the direction instantly.

Is the acre to hectare conversion exact?

Yes. A hectare is exactly 10,000 square meters — the area of a 100 m × 100 m square. That fixed definition is what the converter above uses, so any rounding you see is a display choice, not a limitation of the math.

Acres to Hectares Converter

Q: What is a acre?

Acre (ac) measures area. The international acre is defined as exactly 4,046.8564224 square meters. It is classified as a US/imperial customary unit.

Q: What is a hectare?

Hectare (ha) measures area. A hectare is exactly 10,000 square meters — the area of a 100 m × 100 m square. It is classified as a non-SI metric unit accepted for use with SI.

About Converting Acres to Hectares

Acre and Hectare both measure a farming-related quantity — a land area or an application/yield rate per unit area — used to report crop yields, calculate how much fertilizer or seed a field needs, and plan irrigation. Acre is typically associated with united States, while Hectare is typically associated with used worldwide, especially in agriculture, forestry, and land statistics outside the US.

Formula

hectares = acres × 0.40468564224

This factor comes from each unit's defined relationship to the category's base unit: 1 acre equals 4046.8564224 base units, and 1 hectare equals 10000 base units, so dividing one by the other gives the direct acre-to-hectare factor of 0.40468564224.

Simple example

1 ac × 0.4046856422 = 0.4046856422 ha

1 acre = 0.4046856422 hectares.

Real-world example

100 ac × 0.4046856422 = 40.46856422 ha

100 acres = 40.46856422 hectares.

Conversion table

Acre (ac)	Hectare (ha)
1 ac	0.4046856422 ha
5 ac	2.023428211 ha
10 ac	4.046856422 ha
50 ac	20.23428211 ha
100 ac	40.46856422 ha
500 ac	202.3428211 ha

Reverse conversion: Hectare to Acre

0.4046856422 ha × 2.471053815 = 0.9999999999 ac

0.4046856422 hectares = 0.9999999999 acres.

acres = hectares × 2.47105381467

For a page dedicated to this direction, see Hectare to Acre.

Acre vs. Hectare

Aspect	Acre	Hectare
Family	US/imperial customary unit	non-SI metric unit accepted for use with SI
Typical use	Measuring farmland, ranch, and rural property size in the US	Reporting farmland and crop area in international agricultural statistics
Where it's used	United States	Used worldwide, especially in agriculture, forestry, and land statistics outside the US

Understanding the Acre

Acre (ac) measures area. The international acre is defined as exactly 4,046.8564224 square meters. It is classified as a US/imperial customary unit.

Where it's used: United States United Kingdom (informal/historical, land registry legacy) Countries with historical British land-survey systems

International acre vs. US survey acre. The US survey acre, based on the US survey foot, differs from the international acre by about two parts per million. The US retired the survey foot/acre for federal use at the end of 2022.

Uses of the Acre today

Measuring farmland, ranch, and rural property size in the US
Real estate listings and zoning for land parcels
Forestry and land-management reporting

History of the Acre

The acre originated in medieval England as a practical field measurement: the area a yoke of oxen could plow in one day, roughly a furlong (660 ft) long by a chain (66 ft) wide, giving the 43,560 square feet still used today.

Edward I's 1305 statute formalized this figure. In 1959, the same International Yard and Pound Agreement that fixed the pound also fixed the international acre at exactly 4,046.8564224 m², though the US separately retained a slightly different 'US survey acre' for some legacy land records until it was phased out in 2023.

Historical origin. Acre was not the invention of a single named person; it developed through the process described above.

Understanding the Hectare

Hectare (ha) measures area. A hectare is exactly 10,000 square meters — the area of a 100 m × 100 m square. It is classified as a non-SI metric unit accepted for use with SI.

Where it's used: Used worldwide, especially in agriculture, forestry, and land statistics outside the US

Uses of the Hectare today

Reporting farmland and crop area in international agricultural statistics
Forestry and land-use planning
Real estate and cadastral survey in metric countries

History of the Hectare

The hectare derives from the 'are,' a metric area unit (100 m²) introduced during the French Revolutionary metric reforms of the 1790s. 'Hecto-' is simply the SI prefix for 100, so a hectare is 100 ares.

Although not itself an SI unit, the hectare is officially accepted for use alongside SI units by the BIPM because of its practical importance in land measurement, and it remains the standard land-area unit in most of the world.

Historical origin. Hectare was not the invention of a single named person; it developed through the process described above.

Acre — sources

NIST — US Survey Foot: Revised Unit Conversion Factors — Documents the 1959 international acre definition and the 2022/2023 survey-foot retirement.

Hectare — sources

BIPM SI Brochure, 9th edition — Non-SI units accepted for use with SI — Lists the hectare as an accepted non-SI unit.

Acres to Hectares Converter — ac to ha

Agriculture Converter