Barns to Square Miles (b to mi²)
1 barn equals 3.861021585×10⁻³⁵ square miles (rounded).
How to convert barns to square miles
To convert barns to square miles, multiply the number of barns by 3.861021585×10⁻³⁵. The factor is rounded to 10 significant digits. To go the other way, multiply square miles by 2.58998811×10³⁴ (rounded).
square miles = barns × 3.861021585×10⁻³⁵
Example: 10 barns = 3.861021585×10⁻³⁴ square miles.
About these units
Barn (b)
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
Square Mile (mi²)
640 acres or about 2.59 km². Used for the area of cities, states and countries in the US and UK.
A thousand Roman paces, mille passus, became the mile, and under Elizabeth I Parliament fixed the statute mile at eight furlongs, or 5,280 feet, in place of the older Roman-based value. The square mile inherits that length. Its most famous use came in the United States: the Land Ordinance of 1785 started the Public Land Survey System so that western land could be surveyed and sold to pay war debts, beginning with the Seven Ranges in eastern Ohio.
In that system a section is roughly one square mile, or 640 acres, and a township is 36 sections in a square six miles on a side. One square mile is nearly 2.59 million square meters. Chicago's Midway International Airport, at about 650 acres, covers roughly 1.02 square miles. Beware the phrase mile square: a region 20 miles square has 400 square miles, but so does a rectangle 10 by 40 miles. The US survey version of the mile was retired from 1 January 2023, but the international square mile remains the unit for cities, states and countries in the US and UK.
1 square mile = 2,589,988.11 square meters (approximately).
Sources: Wikipedia: Square mile; Wikipedia: Public Land Survey System; Wikipedia: Mile
Related conversions
- Square miles to barns (reverse)
- Barns to square meters
- Barns to square kilometers
- Barns to hectares
- Barns to square inches
- Barns to square feet
- Barns to square yards
- Barns to acres
- Square meters to square miles
- Square kilometers to square miles
- Hectares to square miles
- Square inches to square miles
- Square feet to square miles
- Square yards to square miles
- Acres to square miles
- Square centimeters to square miles
- Square millimeters to square miles
- Tsubo to square miles
- Pyeong to square miles
- Rai (Thai) to square miles
See all area units.