Hectares to Barns (ha to b)

1 hectare equals 1×10³² barns exactly.

1 hectare = 1×10³² barns

How to convert hectares to barns

To convert hectares to barns, multiply the number of hectares by 1×10³². This factor is exact. To go the other way, multiply barns by 1×10⁻³².

barns = hectares × 1×10³²

Example: 10 hectares = 1×10³³ barns.

About these units

Hectare (ha)

Metric (SI)Current unit

10,000 square meters (2.471 acres). The standard unit for land and agricultural areas outside the US.

Hecto plus are: the name was coined in French, and are itself comes from the Latin area, meaning an open space. The French law of 18 Germinal, Year III (7 April 1795) defined the are as 100 square meters, and the hectare followed as 100 ares, or 10,000 square meters. The unit is therefore a product of the original French metric reforms rather than of later SI work, which is one reason its official status has always been slightly awkward.

When the SI was set up in 1960 the are was not recognized, and the hectare was classed as a non-SI unit accepted for use with it. In practice it is the standard unit for land ownership, planning and agriculture in the European Union, the United Kingdom, Canada, Australia, New Zealand and South Africa, while the United States and Myanmar stay with the acre. A hectare is a square 100 meters on each side, about the size of Trafalgar Square, and equals roughly 2.47 acres. One hundred of them make a square kilometer.

1 hectare = 10,000 square meters (exactly).

Sources: Wikipedia: Hectare; Wikipedia: Are (unit); NIST Guide to the SI, Appendix B.8: conversion factors

Barn (b)

ScientificCurrent unit

Exactly 10⁻²⁸ square meters. Used in nuclear and particle physics for reaction cross-sections; the name is a joke about a target 'as big as a barn'.

Nuclear physicists coined this unit during the Second World War. Marshall Holloway and Charles Baker, working at Purdue on Manhattan Project problems, wanted a short name for the cross section of a nucleus and passed over names such as Oppenheimer and Bethe. They settled on a joke about a target that was really as big as a barn, and the word first appeared in print in a secret Los Alamos report of June 1943.

One barn is 10 to the power of minus 28 square meters, or 100 square femtometers, roughly the cross-sectional area of a uranium nucleus. NIST lists the conversion as exact. The barn was never an SI unit, though the BIPM acknowledged it in the eighth SI Brochure because particle physics relies on it. Prefixed forms dominate today: the femtobarn is the usual choice in high-energy physics, and the inverse femtobarn measures integrated luminosity. Informal names exist too, such as outhouse for a microbarn and shed for a yoctobarn.

1 barn = 1×10⁻²⁸ square meters (exactly).

Sources: Wikipedia: Barn (unit); NIST SP 811, Appendix B.8 conversion factors

Related conversions

See all area units.