Square Millimeter to Hectare Converter

and Standards

The hectare is defined as an area of exactly 10,000 square meters:

1 ha = 10,000 m² = 100 m × 100 m

Precise Equivalents

• 1 ha = 10,000 m² (exactly, by definition)
• 1 ha = 0.01 km² = 1/100 square kilometer (exactly)
• 1 ha = 100 ares (where 1 are = 100 m²)
• 1 ha = 1 hm² (square hectometer)
• 1 ha = 2.47105 acres (US survey/international)
• 1 ha = 107,639.1 square feet
• 1 ha = 11,959.9 square yards
• 1 ha = 15,500,000 square inches

The hectare derives from the are (symbol: a), a rarely used metric unit defined as 100 m². The prefix hecto- means "hundred," so hectare literally means "hundred ares."

SI Status

The hectare is not an official SI unit—the SI unit of area is the square meter (m²). However, the International Bureau of Weights and Measures (BIPM) explicitly lists the hectare as a non-SI unit accepted for use with the SI in its SI Brochure, recognizing its overwhelming practical importance in land measurement globally.

Metric Prefixes and Multiples

While technically compatible with metric prefixes, only a few are used in practice:

• Decare (daa) = 0.1 ha = 1,000 m² (used in some Eastern European and Middle Eastern countries)
• Hectare (ha) = 1 ha = 10,000 m² (standard unit)
• Square kilometer (km²) = 100 ha (preferred for very large areas)

The centiare (1 m²) and are (100 m²) exist theoretically but are rarely used today.

and Evolution

The French Revolution and the Birth of the Metric System (1790s)

The hectare emerged from the revolutionary fervor of 1790s France. The French Revolution sought to overthrow not only the monarchy but also the chaotic patchwork of traditional measurement units that varied by region, trade, and lord. Land measurement was particularly inconsistent: the arpent varied from 34 to 51 ares depending on locality, and dozens of other regional land units created confusion and inequity.

In 1795, the revolutionary government adopted the metric system, including the are as the fundamental unit of land area, defined as 100 square meters (a square 10 meters on each side). The hectare ("hundred ares") was immediately created as a larger, more practical unit for agricultural land, equal to 10,000 square meters—a square 100 meters on each side.

The Triumph of the Hectare over the Are (19th Century)

While the are was the official base unit, it proved awkwardly small for practical agriculture and forestry. A typical farm field might be dozens or hundreds of ares. The hectare, by contrast, was the perfect size: small enough to measure individual fields precisely, large enough to describe farm sizes conveniently. Within decades, the hectare became the dominant unit, and the are faded into obscurity.

Key milestone: In 1879, the International Committee for Weights and Measures (CIPM) formally adopted the hectare for international use, cementing its status as the global standard for land measurement.

Global Metrication: The Hectare Spreads Worldwide (1800s-1900s)

As the metric system spread from France across Europe, Latin America, and eventually Asia and Africa, the hectare went with it:

• 1800s: Adopted across continental Europe (Germany, Italy, Spain, Netherlands, Scandinavia)
• 1900-1950: Latin American countries metricated (Argentina, Brazil, Mexico, Chile)
• 1950-1980: Post-colonial nations in Africa and Asia adopted the metric system, including the hectare (India, Indonesia, Nigeria, Kenya)
• 1970s: Australia and New Zealand officially switched from acres to hectares
• 1980s-present: Even partially metricated countries like Canada and the UK increasingly use hectares for official land statistics

Modern status: As of 2025, the hectare is the primary land measurement unit in over 170 countries, representing more than 95% of the world's population and land area.

Notable Holdouts and Hybrid Systems

United States: Continues to use acres almost exclusively for land measurement, despite metrication in science and industry.

United Kingdom: Officially metricated in the 1990s, but acres persist in casual speech, real estate listings, and tradition. Government statistics use hectares, while property advertisements often show both units.

Myanmar: Uses traditional Burmese land units alongside acres; hectares are rare.

Canada: Officially metricated (hectares), but older Canadians and rural areas often still reference acres informally.

The Hectare in International Agriculture and Forestry

By the mid-20th century, international organizations standardized on the hectare:

• FAO (Food and Agriculture Organization): Reports global agricultural data in hectares
• World Bank: Land area statistics in hectares
• IPCC and climate science: Forest cover, deforestation, and carbon storage measured in hectares
• International land treaties: Boundary agreements, protected areas, and resource rights defined in hectares

The hectare's dominance in these domains ensures its continued relevance even in non-metric countries, where professionals in agriculture, forestry, and environmental science routinely convert between acres and hectares.

1. Agriculture: Farm Sizes and Crop Yields

The hectare is the universal standard for agricultural land measurement worldwide (except in the US). Farm sizes, field areas, crop yields, and agricultural statistics are expressed in hectares.

Crop yields are standardized as metric tons per hectare (t/ha) or kilograms per hectare (kg/ha):

• Wheat: 3-10 t/ha (depending on region and farming intensity)
• Rice: 4-8 t/ha
• Corn (maize): 8-15 t/ha
• Soybeans: 2-5 t/ha

Example: A 50-hectare wheat farm yielding 5 t/ha produces 250 metric tons of wheat annually.

2. Forestry: Timber Yields and Forest Management

Forestry professionals measure forest areas, logging concessions, reforestation projects, and timber yields in hectares.

Timber yield is expressed as cubic meters per hectare (m³/ha):

• Temperate softwood forest: 150-400 m³/ha
• Tropical rainforest: 200-600 m³/ha
• Boreal forest: 80-200 m³/ha

Example: A sustainable logging operation might harvest 5 m³/ha/year from a 1,000-hectare forest, yielding 5,000 m³ of timber annually.

3. Urban Planning: Zoning and Development

Urban planners use hectares to measure development sites, zoning areas, and infrastructure projects. Residential density is often expressed as dwellings per hectare (dw/ha) or persons per hectare (pp/ha).

Typical densities:

• Suburban single-family: 10-25 dw/ha
• Urban townhouses: 30-60 dw/ha
• Mid-rise apartments: 100-200 dw/ha
• High-rise urban core: 300-1,000+ dw/ha

Example: A 20-hectare mixed-use development with an average density of 80 dw/ha would contain 1,600 dwellings.

4. Real Estate: Land Sales and Property Listings

In metricated countries, land parcels are listed in hectares. Small properties (under 1 ha) may be listed in square meters, while large rural properties use hectares.

Example listing: "50-hectare vineyard estate in Tuscany, fully planted, irrigation, farmhouse included."

In hybrid countries like the UK and Canada, listings often show both units: "25 hectares (62 acres)."

5. Environmental Science: Protected Areas and Deforestation

Conservation organizations, national parks, and environmental treaties use hectares to define protected areas, measure deforestation, and calculate carbon storage.

Carbon storage in forests is measured as metric tons of CO₂ equivalent per hectare (tCO₂e/ha):

• Tropical rainforest: 200-600 tCO₂e/ha
• Temperate forest: 100-300 tCO₂e/ha
• Boreal forest: 50-150 tCO₂e/ha

Example: Protecting 10,000 hectares of Amazon rainforest prevents release of ~4,000,000 metric tons of CO₂.

6. International Development and Food Security

The Food and Agriculture Organization (FAO), World Bank, and UN agencies report agricultural land, arable land per capita, and food production in hectares.

Arable land per capita (global average): ~0.19 ha per person (2025)

• High: Australia ~1.9 ha/person, Canada ~1.2 ha/person
• Low: Bangladesh ~0.05 ha/person, China ~0.08 ha/person

Food security context: Feeding one person for a year requires approximately 0.2-0.3 ha of arable land (depending on diet and farming intensity).