Square Inches to Barns (in² to b)

1 square inch equals 6.4516×10²⁴ barns exactly.

1 square inch = 6.4516×10²⁴ barns

How to convert square inches to barns

To convert square inches to barns, multiply the number of square inches by 6.4516×10²⁴. This factor is exact. To go the other way, multiply barns by 1.5500031×10⁻²⁵ (rounded).

barns = square inches × 6.4516×10²⁴

Example: 10 square inches = 6.4516×10²⁵ barns.

About these units

Square Inch (in²)

US & ImperialCurrent unit

A square one inch on a side, exactly 6.4516 cm². Used for small parts and for pressure (pounds per square inch).

Latin uncia, one twelfth, gave English the inch, which Old English borrowed as ynce. A statute of Edward II in 1324 defined it as three barleycorns, dry and round, set end to end, and the barleycorn remained the base for centuries after 1066. The modern square inch rests on a 20th-century agreement: the United States adopted a yard of exactly 0.9144 meter on 1 July 1959, the United Kingdom followed effective 1 January 1964, and the inch became exactly 25.4 mm.

Squaring that gives exactly 6.4516 cm² for one square inch, and one square meter is about 1,550 of them. Its best-known descendant is the pound per square inch, psi, the pressure unit still used for American tires and air tanks: atmospheric pressure at sea level is about 14.7 psi, a car tire is typically inflated to around 32 psi above the surrounding air, and one psi is about 6.895 kilopascals. The square inch itself is common in the US and UK for small parts and printed material.

1 square inch = 0.00064516 square meters (exactly).

Sources: Wikipedia: Square inch; Wikipedia: Inch; Wikipedia: Pounds per square inch

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

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