barn

Non-SI unit

Name	Symbol	Quantity	Expressed in terms of SI base units		Expressed in terms of other SI units
barn	b	area	10−28 m2		100 fm2 (10−12 cm)2
Definition The barn, symbol b, is a non-SI unit of area. One barn is equal to 10−28 m2, or 100 fm2.

Particle physics

The barn is a non-SI unit of cross-section used in nuclear and particle interactions.