Acres to Hectares Converter
Convert between acres and hectares — bidirectional, exact, no rounding tricks. 1 acre = 0.40468564224 ha; 1 ha = 2.4710538147 acres.
1 acres =
0.4
Converted via exact SI factors: 1 acre = 4046.8564224 m² (43 560 ft² under the 1959 International Yard and Pound Agreement, 1 yd = 0.9144 m exactly) and 1 hectare = 10 000 m² exactly (BIPM). So 1 acre = 0.40468564224 ha and 1 hectare = 2.4710538147 acres. 1 acres × 0.4046856422 = 0.40468564224000003 hectares.
How to use this calculator
Type a value, pick "Acres → Hectares" or "Hectares → Acres" in the Direction select, and the result updates instantly. Flip the direction to invert the conversion.
How the calculation works
Both factors are exact. 1 acre is defined as 43 560 square feet, and under the 1959 International Yard and Pound Agreement 1 yard = 0.9144 m exactly, so 1 acre = 43 560 × (0.3048)² m² = 4046.8564224 m². 1 hectare is defined by BIPM as exactly 10 000 m² (a square 100 m on a side). The ratio 4046.8564224 / 10 000 = 0.40468564224 gives hectares per acre, and the reciprocal 2.4710538147 gives acres per hectare.
Worked example
A 5-acre paddock in hectares: 5 × 0.40468564224 = 2.0234282112 ha. Going back: 2.0234282112 × 2.4710538147 = 5 acres exactly, demonstrating the round-trip.
Frequently asked questions
How many hectares are in an acre?
1 acre = 0.40468564224 hectares exactly. The factor is exact because both units are defined in SI base units: 1 acre = 43 560 ft² and 1 ft = 0.3048 m exactly.
How many acres are in a hectare?
About 2.4710538147 acres. A hectare is a square 100 m on a side (10 000 m²), which is roughly 2.47 times larger than an acre.
Where is the acre used and where is the hectare used?
The acre is the standard land unit in the United States, the United Kingdom (informally — Land Registry uses hectares), Ireland, and parts of South Asia. The hectare is the standard agricultural and cadastral unit almost everywhere else, including the EU, Australia, New Zealand, Canada, and most of Africa and Latin America.
Is the US survey acre the same as the international acre?
They differ in the eleventh significant digit. The international acre (used here) is exactly 4046.8564224 m². The US survey acre, retired by NIST on 1 January 2023, was 4046.872609... m² — a difference of about 16 mm² per acre. For all practical conversion this is invisible.
Why does a hectare equal 10 000 m²?
The hectare is defined as a square hectometre — 100 m × 100 m. "Hecto" is the SI prefix for 100, and "are" is an obsolete SI-derived unit equal to 100 m². So 1 hectare = 100 ares = 10 000 m² by construction.
How accurate is this converter?
It uses the exact NIST/SI factor 0.40468564224 in IEEE 754 double precision. The only rounding happens at display; the underlying math is good to roughly 15 significant figures, far beyond what any land measurement can reach.