science

Hectare

Hectare is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Hectare rather than just read about it. In short: The hectare (; SI symbol: ha) is a non-SI metric unit of area equal to a square with 100-metre sides (1 hm2), that is, 10,000 square metres (10,000 m2), and is primarily used in the measurement of land. There are 100 hectares in one square kilometre.

Key takeaways

Hectare belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Hectare to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Hectare from memory before moving on to harder problems.

Reference excerpt

The hectare (; SI symbol: ha) is a non-SI metric unit of area equal to a square with 100-metre sides (1 hm2), that is, 10,000 square metres (10,000 m2), and is primarily used in the measurement of land. There are 100 hectares in one square kilometre. An acre is about 0.405 hectares and thus one hectare is about 2.47 acres.

In 1795, when the metric system was introduced, the are was defined as 100 square metres, or one square decametre, and the hectare ("hecto-" + "are") was thus 100 ares or ⁠1/100⁠ km2 (10000 square metres). When the metric system was further rationalised in 1960, resulting in the International System of Units (SI), the are was not included as a recognised unit, and from 2026 the hectare is no longer described by the International Bureau of Weights and Measures (BIPM) as accepted for use with the SI.

Description

The name was coined in French, from the Latin ārea. The hectare is equivalent to 10,000 square metres (a square hectometre). It is widely used throughout the world for the measurement of large areas of land, and it is the legal unit of measure in some domains concerned with land ownership, planning, and management, including law (land deeds), agriculture, forestry, and town planning throughout the European Union, South Africa, New Zealand, Australia, Canada and the United Kingdom. However, the United States and Myanmar (Burma) use the acre instead of the hectare for measuring surface or land area. In many countries, metrification redefined or clarified existing measures in terms of metric units. The following legacy units of area have been redefined as being equal to one hectare:

Jerib (Persian: جریب) in Iran Djerib (Turkish: cerip) in Turkey Gongqing (traditional Chinese: 公頃; simplified Chinese: 公顷; pinyin: gōngqǐng) in China Manzana in Argentina Bunder in the Netherlands (until 1937) In Mexico, land area measurements are commonly given as combinations of hectares, ares, and centiares. These are commonly written separated by a hyphen; for example, 1-21-00.26 ha would mean 1 hectare, 21 are, and 0.26 centiare (12100.26 m2).

History The metric system of measurement was first given a legal basis in 1795 by the French Revolutionary government. The law of 18 Germinal, Year III (7 April 1795) defined five units of measure:

The metre for length The are (100 m2) for area [of land] The stère (1 m3) for volume of stacked firewood The litre (1 dm3) for volumes of liquid The gram for mass In 1960, when the metric system was updated as the International System of Units (SI), the are did not receive international recognition. The International Committee for Weights and Measures (CIPM) used to classify the hectare as a "Non-SI unit accepted for use with the International System of Units" but As of 2026, the International Bureau of Weights and Measures (BIPM) no longer describes it and other widely used non-SI units as accepted. In 1972, the European Economic Community (EEC) passed directive 71/354/EEC, which catalogued the units of measure that might be used within the Community. The units that were catalogued replicated the recommendations of the CGPM, supplemented by a few other units including the are (and implicitly the hectare) whose use was limited to the measurement of land.

Unit family

The names centiare, deciare, decare and hectare are derived by adding the standard metric prefixes to the original base unit of area, the are.

Decimilliare The decimilliare (dma, sometimes seen in cadastre area evaluation of real estate plots) is ⁠1/10,000⁠ are or one square decimetre. Such usage of a double prefix is non-standard. The decimilliare is (100 mm)2 or roughly a four-inch-by-four-inch square. (The decimilliare is smaller by approximately 3.1%.)

Centiare The centiare is one square metre.

Deciare The deciare (rarely used) is ten square metres.

Are The are (, ) is a unit of area, equal to 100 square metres (10 m × 10 m), used for measuring land area. It was defined by older forms of the metric system, but is now outside the modern International System of Units (SI). It is still commonly used in speech to measure real estate, in particular in Indonesia, India, and in various European countries. In Russian and some other languages of the former Soviet Union, the are is called sotka (сотка: 'a hundred', i.e. 100 m2 or ⁠1/100⁠ hectare). It is used to describe the size of suburban dacha or allotment garden plots or small city parks where the hectare would be too large. Many Russian dachas are 6 ares in size (in Russian, шесть соток).

Decare The decare or dekare () is derived from deca and are, and is equal to 10 ares or 1000 square metres. It is used in Norway and in the former Ottoman areas of the Middle East and Bulgaria as a measure of land area. The names of the older land measures of similar size are usually used, redefined as exactly one decare:

Stremma in Greece Dunam, dunum, dulum, donum, or dönüm in the Balkans, Israel, Palestine, Jordan, Lebanon, Syria, and Turkey Mål in Norway.

Conversions

The most commonly used units are in bold. One hectare is also equivalent to:

1 square hectometre 1.008 chō (Japan) 2.381 feddan (Egypt) 6.25 rai (Thailand) 10 dunam or dönüm (Middle East) 10 stremmata (Greece) 15 mǔ or 0.15 qǐng

Unicode The Unicode character U+33CA ㏊ SQUARE HA, in the CJK Compatibility block, is intended for compatibility with pre-existing East Asian character codes. It is not intended for use in alphabetic contexts. U+3336 ㌶ SQUARE HEKUTAARU is a combination of ヘクタール (hekutāru), the Japanese translation of "hectare".

See also Conversion of units Hectometre Order of magnitude

References

External links

Illustrations

Worked examples

Example 1 — a first encounter with Hectare

Start with the simplest possible case. Write down what Hectare claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Hectare before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Hectare ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Hectare

In research: Hectare appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Hectare in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Hectare is common in secondary-school and first-year university syllabi. It links to neighbouring topics Non-SI metric units, Units of area, so understanding it makes those chapters shorter.
In everyday life: Look for Hectare outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Hectare in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Hectare means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Hectare out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Hectare in simple terms?

Why does Hectare matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Hectare?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Hectare.