Convert Barns to Square Millimeters
Convert Barns (b) to Square Millimeters (mm²) instantly and accurately.
Conversion Formula
mm² = b × 1.000000000e-22
About Barns
A barn (b) is a unit of area used in nuclear and particle physics to measure effective cross-sections of atomic nuclei and particle interaction probabilities. Equal to 10⁻²⁸ m² (10⁻²⁴ cm²), it was humorously named during the Manhattan Project - physicists joked that uranium nuclei were 'as big as a barn' at the subatomic scale. Particle physics experiments at accelerators like CERN report cross-sections in millibarns (mb), microbarns (μb), nanobarns (nb), and femtobarns (fb).
About Square Millimeters
A square millimeter (mm²) is a metric unit of area equal to a square with sides of one millimeter. It is commonly used in precision engineering, electronics, and measuring very small surfaces such as microchips or printed circuit boards. To visualise: a typical pinhead has an area of about 2-3 mm². This unit is essential in microscopy, medical imaging, and manufacturing where tiny, precise measurements are critical.
Quick Reference Table
| Barns (b) | Square Millimeters (mm²) |
|---|---|
| 1 b | 1 × 10-22 mm² |
| 2 b | 2 × 10-22 mm² |
| 5 b | 5 × 10-22 mm² |
| 10 b | 1 × 10-21 mm² |
| 25 b | 2.5 × 10-21 mm² |
| 50 b | 5 × 10-21 mm² |
| 100 b | 1 × 10-20 mm² |