Acres to Hectares Converter

The acres to hectares converter is a free, two-way area calculator that switches between the imperial / US customary acre and the metric hectare in a single step, with square metres shown alongside because farmland, real estate, and planning documents almost always quote areas in m² as well. Type a value in either field, acres or hectares, and the other field updates instantly. The math is anchored to the definitions of the two units themselves: 1 acre = 4046.8564224 m² exactly, and 1 hectare = 10 000 m² exactly. Because both units are defined in terms of square metres, dividing one by the other gives an exact conversion factor with no rounding error beyond the precision you choose to display. Whether you are reading a US farm listing, comparing European land prices, sizing a sports field, or quoting a forestry parcel, this calculator gives the same number any reference text will give you.

The acre is still used in the United States, the United Kingdom (for some purposes), Canada, India, Australia, and many Commonwealth countries. The hectare is the metric unit of area most countries use for land, agriculture, forestry, and planning, it is the only common metric area unit that is not a multiple of the square metre by a power of ten (1 ha = 10 000 m² exactly). Both units show up everywhere land is bought, sold, leased, surveyed, or described.

How to Use the Acres to Hectares Converter

1. Type a value in the acres field. The default value is 1 acre, which equals 0.404686 hectares.
2. Watch the hectares field update instantly as you type. The conversion uses the exact factor 1 acre = 0.40468564224 hectares.
3. Or type a value in the hectares field. The acres field will update instantly using the same exact ratio.
4. Read both values in the result box below the inputs. The acres result, the hectares result, and the square-metre equivalent are all shown together, rounded to six decimal places (or to the nearest whole m² for the m² line).
5. Use the Swap button to switch the direction of the conversion, or Copy buttons to put either result on the clipboard.

the Acres To Hectares runs entirely in your browser. Your inputs never leave your device, and there is no rate limit, no sign-up, and no data collection.

The Formulas

Acres to hectares, multiply the acre value by the exact factor 0.40468564224:

hectares = acres × 0.40468564224

This factor is exact, derived directly from the two definitions: 1 acre = 4046.8564224 m² exactly, and 1 hectare = 10 000 m² exactly, so 1 acre = 4046.8564224 / 10 000 = 0.40468564224 hectares with no rounding. For a 100 acre farm, the math is 100 × 0.40468564224 = 40.468564 ha.

Hectares to acres, multiply the hectare value by the exact reciprocal 2.4710538147:

acres = hectares × 2.4710538147   (rounded)
acres = hectares × (10 000 / 4046.8564224)   (exact)

The displayed factor 2.4710538147 acres per hectare is the rounded version of the exact ratio 10000 / 4046.8564224 = 2.4710538146716537... For a 50 ha block of forest, the math is 50 × 2.4710538147 = 123.5527 acres.

Acres to square metres, multiply the acre value by 4046.8564224 exactly:

square_metres = acres × 4046.8564224

This is the definition of the acre in SI units, traced back through the 1959 international yard and pound agreement. For a 5 acre smallholding, the area is 5 × 4046.8564224 = 20 234.28 m².

Hectares to square metres, multiply by 10 000 exactly:

square_metres = hectares × 10 000

This is the definition of the hectare: 1 ha = 100 m × 100 m.

Inverse check, the two factors are reciprocals of each other:

1 acre × 0.40468564224 = 0.40468564224 ha
0.40468564224 ha × 2.4710538147 = 1 acre (to display rounding)

Quick mental shortcuts, for rough estimates, 1 acre ≈ 0.4 ha, and 1 ha ≈ 2.5 acres. So a 10 acre property is roughly 4 ha, and a 100 ha farm is roughly 250 acres. These approximations are within 1 to 2% of the exact value, fine for everyday conversation but not for title deeds or anything that needs to be accurate to the square metre.

Worked Examples

Example 1, Convert 1 acre to hectares (a basic sanity check).

1. Apply the acre-to-hectare factor: hectares = 1 × 0.40468564224.
2. Compute: 1 × 0.40468564224 = 0.40468564224.
3. Round to six decimal places: 0.404686 ha.

1 acre is exactly 0.404686 ha to six decimal places. This is the canonical conversion factor used in most calculators and reference tables, and it is the default starting value of this tool.

Example 2, Convert 100 acres to hectares (a US Midwest farm).

1. Apply the acre-to-hectare factor: hectares = 100 × 0.40468564224.
2. Compute: 100 × 0.40468564224 = 40.46856422.
3. Round to six decimal places: 40.468564 ha.

A 100 acre US Midwest farm is 40.468564 ha, or 404 685.64 m². US farm subsidies and commodity prices are usually quoted in acres and bushels, while European comparisons use hectares and tonnes, being able to convert quickly matters when reading either side of the trade press.

Example 3, Convert 1 hectare to acres (a European allotment garden).

1. Apply the hectare-to-acre factor: acres = 1 × 2.4710538147.
2. Compute: 1 × 2.4710538147 = 2.4710538147.
3. Round to six decimal places: 2.471054 acres.

1 hectare is exactly 2.471054 acres to six decimal places, or 10 000 m². A typical UK allotment garden is about 250 m² (10 poles), so a 1 ha site would host about 40 such plots.

Example 4, Convert 640 acres to hectares (one square mile).

1. Apply the acre-to-hectare factor: hectares = 640 × 0.40468564224.
2. Compute: 640 × 0.40468564224 = 258.9988110336.
3. Round to six decimal places: 258.998811 ha.

640 acres, a US public-land-survey section, is 258.998811 ha. The US township grid divides land into 36 sections of 1 square mile each, so 1 township is roughly 93.24 km² or 23 040 acres.

Example 5, Convert 0.5 acres to hectares (a small residential lot).

1. Apply the acre-to-hectare factor: hectares = 0.5 × 0.40468564224.
2. Compute: 0.5 × 0.40468564224 = 0.20234282112.
3. Round to six decimal places: 0.202343 ha.

A 0.5 acre suburban lot is 0.202343 ha, or about 2 023.43 m², just under a fifth of a hectare. US suburban lots of this size are common in newer subdivisions built after the 1990s.

Where Acres and Hectares Show Up

Both units are used in agriculture, real estate, planning, conservation, and sport, and most documents cross-reference both.

• Agriculture and farming. Crop yields are quoted per acre in the US (bushels per acre) and per hectare in most of the world (tonnes per hectare). A US farmer comparing a 60 bu/ac corn yield to a European 10 t/ha corn yield needs both area units to make the comparison meaningful.
• Real estate and land sales. US residential and rural land is sold by the acre; Australian, Canadian, and continental European rural land is sold by the hectare. Cross-border listings routinely need both numbers.
• Forestry and conservation. Forest stands, national parks, and nature reserves are quoted in hectares almost everywhere, Yellowstone is 898 317 ha, Kruger is about 1 948 528 ha, the Amazon is roughly 550 million ha. US and Canadian forestry still uses acres in some contexts.
• Sports fields. A regulation association football (soccer) pitch is about 0.64 to 0.825 ha (1.58 to 2.04 acres). A cricket ground is about 1.5 ha (3.7 acres). A North American football field is roughly 0.57 ha (1.4 acres).
• Planning and zoning. Planning permissions and lot coverage rules are quoted per hectare in metric countries and per acre in US/UK contexts. Cross-jurisdiction planning documents routinely quote both.
• Surveying and cadastral records. US land is divided into townships, sections, and aliquot parts (each section is 640 acres ≈ 259 ha). Most other countries record land in hectares or m².

Common Mistakes to Avoid

• Treating the conversion factor as approximate. Some online sources round 1 acre to 0.4047 ha or 1 ha to 2.47 acres instead of using the exact values. For legal documents, agricultural subsidy claims, and forestry permits, the small error compounds over large areas. Use at least six decimal places for transactions.
• Mixing up the inverse direction. Acres → ha is ×0.40468564224; ha → acres is ×2.4710538147. Multiplying when you should divide is the single most common conversion mistake.
• Using the wrong acre. The international acre (4046.8564224 m²) is used by NIST and the BIPM, but the US survey acre (4046.872609874252 m²) is slightly larger, about 4 parts per million, and was used in some US state plane coordinate systems. This calculator uses the international acre.
• Forgetting the m² cross-check. A quick sanity check: 1 ha = 10 000 m² and 1 acre ≈ 4047 m². If your converted number doesn't pass that check, you have either mis-typed or mis-multiplied.
• Converting linear units with the area factor. Acres and hectares are areas. A 1 acre lot is not 0.404686 ha wide or long, it is 0.404686 ha in total area. Use a length converter for distances.

Limitations and Assumptions

This calculator uses the international acre (4046.8564224 m² exactly), which is the standard adopted by NIST SP 811 and the 1959 international yard and pound agreement. The hectare is defined by the BIPM as exactly 10 000 m². Both factors are exact by international definition, so the displayed factors (0.40468564224 ha per acre and 2.4710538147 ac per ha) carry the full precision of the underlying definitions. Results are rounded to six decimal places for acres and hectares, and to the nearest whole m² for the square-metre line. For US survey work where the US survey acre (4046.872609874252 m²) is specified, a small (~0.016 m² per acre) discrepancy will appear; use a dedicated surveying calculator for that case.

Quick Reference

• Free to use: yes, no sign-up required.
• Privacy: all calculations run locally in your browser; nothing is sent to a server.
• Units supported: acres, hectares, square metres.
• Precision: results are shown to six decimal places for the unit fields and to the nearest whole m² for the square-metre line.
• Bidirectional: type in either field and the other updates instantly.
• Mobile friendly: the layout adapts to phones, tablets, and desktops.
• Offline: once the page has loaded, the calculator keeps working without a network connection.

Frequently Asked Questions

How many hectares are in an acre?

Exactly 0.40468564224 hectares. This factor is exact because both the acre (4046.8564224 m²) and the hectare (10 000 m²) are defined in terms of square metres by international agreement. To six decimal places, 1 acre = 0.404686 ha.

How many acres are in a hectare?

Exactly 2.4710538146717... acres, usually rounded to 2.471054 for everyday use. This is the exact reciprocal of 0.40468564224, since 1 hectare divided by 1 acre gives 10 000 / 4046.8564224 = 2.4710538146717...

How many square metres are in an acre?

Exactly 4046.8564224 m², traced through the 1959 international yard and pound agreement. To two decimal places, 1 acre = 4046.86 m². The square-metre equivalent is shown alongside the hectare value because land, real estate, and planning documents almost always quote areas in m² as well.

How many square metres are in a hectare?

Exactly 10 000 m², because 1 hectare is defined as 100 m × 100 m by the BIPM. A hectare is the only common metric unit of area that is not a multiple of the square metre by a power of ten.

What is the difference between the international acre and the US survey acre?

The international acre, used by this calculator and by NIST, is exactly 4046.8564224 m². The US survey acre, used historically in some US state plane coordinate systems, is exactly 4046.872609874252 m², about 0.016 m² larger per acre, or about 4 parts per million. The difference is negligible for everyday conversions but shows up in US legal surveying.

Why are both acres and hectares still in use?

The acre survives in the United States, the United Kingdom (for some purposes), Canada, India, Australia, New Zealand, and several other Commonwealth countries because of historical inertia, established legal descriptions, and the volume of existing records. The hectare is the SI accepted unit and is used almost everywhere else for land, agriculture, forestry, and planning. Cross-border trade, international reporting, and online listings routinely need both numbers.

Can I use this converter for square feet or square miles?

No. Square feet and square miles are different units (US customary), and they convert with different factors. 1 acre = 43 560 square feet exactly, and 1 square mile = 640 acres exactly. Use a dedicated area converter for those.

Are UK acres and US acres the same?

Yes. Since 1959, the international yard and pound agreement fixed the acre at exactly 4046.8564224 m² in both the UK and the US. Any historical difference was resolved by the agreement, and the same factor is used everywhere today.

References

• NIST Special Publication 811, Guide for the Use of the International System of Units (SI), which lists the exact conversion factors for the acre in square metres.
• Bureau International des Poids et Mesures (BIPM), The International System of Units (SI), 9th edition, which defines the hectare as exactly 10 000 m².
• ISO 80000-3:2006, Quantities and units, Part 3: Space and time, the international standard for area and related quantities.
• National Geodetic Survey (NGS), Units of Area reference page, which documents the US adoption of the 1959 international yard and pound agreement and the difference between the international acre and the US survey acre.
• The International Yard and Pound Agreement of 1959, signed by the United States, United Kingdom, Canada, Australia, New Zealand, and South Africa, which standardised the inch, foot, yard, pound, and acre at 1 yard = 0.9144 m exactly.
• USDA, Farm Service Agency acreage reporting guidelines, which use acres and hectares interchangeably for cross-border and international reporting.
• United Nations Food and Agriculture Organization (FAO), FAOSTAT database, which reports agricultural land use in hectares with conversions to acres for US-context comparison.

Q: Can the Acres To Hectares be used for professional or commercial purposes? A: Yes, the Acres To Hectares provides mathematically correct results that are suitable for professional, commercial, and educational use. For high-stakes applications (legal land transfers, agricultural subsidy claims, forestry permits), verify results with a licensed surveyor or domain expert. The formulas used are well-established and validated against international standards (NIST, BIPM, ISO 80000-3).

Q: How often are the Acres To Hectares formulas updated? A: The formulas are based on established scientific and metrological references and rarely require updates. Both the acre and the hectare are defined by international agreement in terms of the square metre, so the conversion factor between them is exact and stable. when standards change, the Acres To Hectares is updated to reflect the current authoritative source. The references section above lists the specific sources used.

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