Article — Ares to Hectares Converter
Ares to hectares: the exact 1:100 metric conversion
1 hectare equals exactly 100 ares. The are is a 10 m by 10 m square (100 m²) and the hectare is a 100 m by 100 m square (10,000 m²). Both units were defined in the 1795 French metric reform and remain in use across European land registries today.
Almost every official land record in continental Europe still references one of these two units. Hectares dominate farm subsidies, forestry reports, and national statistics. Ares persist in older property deeds, allotment paperwork, and small-plot sales. The conversion is fixed and exact, so the only thing that matters is which unit is needed for the document.
What ares and hectares measure
The are (symbol a) is a metric unit of area equal to 100 square metres, the area of a square with sides of 10 metres. The hectare (symbol ha) is 100 ares, or 10,000 square metres, the area of a square with sides of 100 metres. Both are decimal-based by design, which means converting between them is a simple shift of the decimal point.
The Bureau International des Poids et Mesures (BIPM) lists the hectare as an accepted non-SI unit for use in land measurement. The are is no longer recommended by the SI but remains legal tender in many European national land laws, including those of Germany, France, and Poland.
The hectare was created because the are was too small to be practical for fields. When the metric system was launched in 1795, surveyors quickly realised that a 100 m² plot would not describe a working farm. Hectare combines the Greek "hekaton" (one hundred) with "are" to deliver a unit one hundred times larger.
History of ares and hectares
Both units came out of the French Revolutionary metric reform of 1795. Reformers wanted decimal units for everything: length (metre), volume (litre), mass (kilogram), and area (are). The are was set at 100 m² because that was a clean square of 10 m by 10 m, perfectly matching the new metre.
The reform faced a problem. Most European farms were already measured in older units that mapped onto hectares cleanly, but the new are was too small to talk about acreage with. By the end of the 19th century, the hectare had become the standard in most metric countries, and the are had drifted to small-plot use only.
ares ÷ 100 = hectareshectares × 100 = ares1 a = 100 m²1 ha = 10,000 m² = 0.01 km²Converting ares to hectares
The conversion is a single arithmetic step. Divide ares by 100 to get hectares; multiply hectares by 100 to get ares. Because the factor is exact, there is no precision loss at any decimal depth. 7 ares is 0.07 hectares. 350 ares is 3.5 hectares. 12.5 hectares is 1,250 ares.
For mental arithmetic, treat ares-to-hectares as a two-place decimal shift to the left. 4,200 a becomes 42.00 ha. 26 a becomes 0.26 ha. The reverse shifts the decimal two places to the right.
Where ares and hectares are still used
Hectares are the global standard for farms, forests, parks, and conservation areas. Eurostat reports EU agricultural land in hectares. The FAO publishes world cropland figures in hectares. Most planning permissions and protected-area registers also use hectares.
Ares survive mostly in small-plot use. German Schrebergarten allotments (the urban garden plots that became famous in the 19th century) are typically 2.5 to 4 ares. Polish dzialki and Czech zahrady, both allotment-garden traditions, run 3 to 8 ares. French jardins ouvriers occupy a similar range. When buying these plots, the area appears in ares on the deed, even if the regional tax record uses hectares or square metres.
- 1 are = 100 m² (10 m × 10 m square)
- 1 hectare = 10,000 m² (100 m × 100 m square)
- 1 hectare = 100 ares (exact)
- 1 hectare = 2.47105 acres
- 1 square kilometre = 100 hectares = 10,000 ares
- EU median farm = 17.4 ha = 1,740 a (2020 Eurostat figure)
Hectares versus acres and square metres
The hectare and acre cover similar ground but are not equivalent. One hectare equals 2.47105 acres, so a 10-hectare farm is about 24.7 acres. Going the other way, one acre is 0.4047 ha, or 40.47 ares. Imperial and metric land sales in Britain often list both numbers side by side because the legal documents still allow either.
The square metre is the only SI-base unit of area. Land records sometimes default to square metres for tiny plots (urban courtyards, terraced houses with small gardens) and switch to hectares for anything larger. The are sits awkwardly between them, which is why it has slowly dropped out of official use.
How big is one hectare?
Picture a 100 m by 100 m square. That is one hectare. For sport: a regulation soccer pitch ranges from 0.62 ha (the FIFA minimum) up to 0.82 ha for the maximum allowed, and a rugby pitch is roughly 1 ha including in-goal areas. An American football field is 0.45 ha including end zones.
For urban scale, the central square of Krakow (Rynek Glowny) is 4.0 ha. Trafalgar Square in London is 1.2 ha. Times Square in New York is 0.4 ha. So one hectare is comfortably bigger than even the largest public squares in many major cities.
For quick agricultural estimates, treat one hectare as 2.5 acres (the true value is 2.47105). The 1.2% error is usually well below the precision of the underlying land survey.
Common ares-to-hectares mistakes
Three errors recur. First, conflating ares with acres because the names look alike. The acre is the imperial unit; the are is the metric unit, and they differ by a factor of 40. A 5-acre plot is 2 ha, but a 5-are plot is only 0.05 ha. Second, forgetting that the prefix matters: hectare means 100 ares, not 1,000 or 10. Third, treating an "are" as if it were a square hectometre. It is not. An are is a square decametre, 100 m², while a square hectometre is 10,000 m² (the hectare).
The unit names differ by one letter but the sizes differ by a factor of about 40. One acre is roughly 40.47 ares. A document that says "5 a" means 500 square metres; "5 acres" means 20,234 square metres. Property sales in Poland and Germany have led to disputes when buyers assume the units interchange.