Convert Acres (ac) to Hectares (ha)

What Is an Acre?

The acre (ac) is a unit of land area in the US customary and British imperial systems, equal to exactly 43,560 square feet or 4,046.856 m². Originally the area a yoke of oxen could plow in one day, it remains the primary land unit in the US, UK (informally), and several former British colonies.

Key equivalences: 1 acre = 43,560 ft² = 4,840 yd² = 1/640 of a square mile.

What Is a Hectare?

The hectare (ha) is a metric unit of area equal to exactly 10,000 square meters — a square with 100-meter sides. Accepted for use with the SI, the hectare is the global standard for reporting land area in agriculture, forestry, and environmental science.

Key equivalences: 1 ha = 10,000 m² = 100 ares = 0.01 km².

Acres to Hectares Formula

The conversion factor is exact:

hectares = acres × 0.40468564224 exact

This comes from dividing the acre's exact metric equivalent (4,046.8564224 m²) by 10,000 m² per hectare. For practical use, acres × 0.405 is accurate to three significant figures.

Worked Example

Convert 27 acres to hectares:

1. Multiply: 27 × 0.40469 = 10.93 ha

So 27 acres ≈ 10.9 hectares. This example appears in the British Columbia Ministry of Agriculture's official conversion factsheet.

Quick Estimation

For mental math, multiply acres by 0.4 — this gives an estimate within 1.2% of the exact value. Alternatively, divide acres by 2.5: 1,000 acres ÷ 2.5 = 400 hectares (exact: 404.7 ha).

Common Conversions at a Glance

Which Is Bigger: Acre or Hectare?

A hectare is about 2.47 times larger than an acre — you need roughly 2½ acres to make one hectare. A hectare covers 10,000 m² (approximately a regulation rugby pitch), while an acre covers 4,047 m² (roughly 75% of an American football field).

When You Need This Conversion

• International agriculture: The US measures farmland in acres, while Europe, South America, Africa, and Asia use hectares. Crop yield comparisons, commodity reports, and international trade data require converting between the two.
• Cross-border real estate: A 100-acre ranch is about 40.5 hectares. Property developers, investors, and appraisers working across US/UK and metric markets need both figures for accurate valuation.
• Environmental science: Deforestation data, protected area designations, and carbon offset programs use hectares internationally, while US-based organizations report in acres.
• Government and land registry: Immigration applications, foreign land ownership regulations, and international treaties may specify land areas in either unit. Accurate conversion prevents legal complications.