Acre to Hectare: Exact Land-Area Conversion
Convert acres to hectares with the exact 0.404686 ha-per-acre relationship, a quick reference table, and the lot and farm sizes where it matters.
The Exact Acre to Hectare Relationship
An acre is defined as 43,560 square feet, which is 4,046.856 square meters. A hectare is exactly 10,000 square meters. Dividing the two gives the exact link: 1 acre = 0.404686 hectare. To convert acres to hectares, multiply by 0.404686.
Our acres to hectares converter does this directly, and our acres to sq ft converter covers square feet.
Quick Reference: Acres to Hectares
Common values
1 acre = 0.4047 ha
5 acres = 2.023 ha
10 acres = 4.047 ha
40 acres = 16.187 ha
100 acres = 40.469 ha
Worked Example
Convert 10 acres to hectares:
10 × 0.404686 = 4.04686 ha. So 10 acres is about 4.05 hectares.
Where Acres and Hectares Matter
US land is measured in acres (homes, farms, ranches), while most of the world uses hectares. A typical suburban lot might be a quarter acre (0.101 ha); a 40-acre farm is about 16.2 hectares. Converting keeps US and international property sizes comparable.
For the bigger picture of the two measurement systems, see our US customary vs metric guide.
Frequently Asked Questions
How many hectares are in an acre?
One acre equals 0.404686 hectare exactly.
How do I convert acres to hectares?
Multiply the acres by 0.404686. For example, 10 acres × 0.404686 = 4.04686 ha.
How many square feet are in an acre?
Exactly 43,560 square feet make 1 acre.
Which is bigger, an acre or a hectare?
A hectare is larger: 1 hectare = 2.47105 acres.
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Quick Summary
One acre equals exactly 0.404686 hectare (43,560 sq ft = 4,046.856 sq m; 1 hectare = 10,000 sq m). Multiply acres by 0.404686 to get hectares: 10 acres ≈ 4.05 ha.
Related Guide
US Customary vs Metric: A Complete Guide to Both Systems
Understand the US customary and metric systems, why the US uses both, and the exact conversion factors that link inches, pounds, and Fahrenheit to their metric equivalents.
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Disclaimer
Unit conversions on this site use internationally recognized, fixed conversion factors (for example, 1 inch = 2.54 cm, 1 pound = 0.45359237 kg, 1 °F = (°C × 9/5) + 32). They are provided for general, informational, and educational use. For applications where accuracy is critical — such as medical dosing, engineering, scientific research, trade, or legal compliance — always verify results against authoritative sources such as the U.S. National Institute of Standards and Technology (NIST) and the official International System of Units (SI) brochure, and follow any applicable local standards.
Exact Constants & Authoritative Sources
Every conversion on this page uses the fixed, internationally agreed constants below — drawn from NIST and the SI Brochure. No values are estimated or rounded as if exact. See the full list on our Sources & Standards page.
- EXACT1 acre = 4046.8564224 square metres (exact, 43,560 ft²)
- EXACT1 hectare (ha) = 10,000 square metres (definition)
- EXACT1 square foot (ft²) = 0.09290304 m² (exact)
- EXACT1 square mile = 2.589988110336 km² (exact)
Common Pitfalls & How to Avoid Them
Acre is not a square
An acre is 43,560 ft² of area in any shape — it can be long and thin. One acre = 4046.86 m² = 0.404686 hectare.
Section vs. hectare
A US "section" is 1 square mile = 259 ha. A hectare (10,000 m²) is ~2.47 acres. Keep the two apart when reading land listings.
A unit-conversion reference site has no manufacturer-specific or device calibration parameters, so "layered tuning" does not apply here. The only real error-handling is input validation: the converter rejects non-numeric, empty, or out-of-range entries and shows a clear message, then falls back to exact constants above. No estimated or rounded figures are ever presented as exact.
Authoritative sources for this page
- NIST (U.S. National Institute of Standards and Technology) — NIST SP 330 — The International System of Units (SI), 2019 edition
- BIPM (International Bureau of Weights and Measures) — SI Brochure — The International System of Units (9th edition)
Last Updated 2026 | This article was reviewed for accuracy