Barn to Square Millimeter Converter
Unit Converter
Instant · Precise · Universal
23 units available
6 categories total
How to Convert Barn to Square Millimeter
To convert barns to m²: multiply by 10⁻²⁸. To fm²: multiply by 100.
1 b = 10⁻²⁸ m² = 100 fm². Millibarns (mb), microbarns (µb), and nanobarns (nb) are common submultiples.
For example, 1 Barn (b) = 1.000000e-22 Square Millimeter (mm²).
Barn to Square Millimeter — Common Values
| Barn (b) | Square Millimeter (mm²) |
|---|---|
| 0.1 | 1.000000e-23 |
| 0.5 | 5.000000e-23 |
| 1 | 1.000000e-22 |
| 2 | 2.000000e-22 |
| 5 | 5.000000e-22 |
| 10 | 1.000000e-21 |
| 25 | 2.500000e-21 |
| 50 | 5.000000e-21 |
| 100 | 1.000000e-20 |
| 500 | 5.000000e-20 |
| 1000 | 1.000000e-19 |
About Barn (b)
Definition
The barn is a unit of area equal to 10⁻²⁸ m², used to express nuclear cross-sections — the effective target area of subatomic particles.
Mathematical Relationship
1 b = 10⁻²⁸ m² = 100 fm². Millibarns (mb), microbarns (µb), and nanobarns (nb) are common submultiples.
Conversion Formula
To convert barns to m²: multiply by 10⁻²⁸. To fm²: multiply by 100.
Practical Applications
Quantifying nuclear reaction probabilities, neutron absorption, and particle scattering in reactor design.
Interesting Facts
The physicists named it 'barn' as a joke: nuclei were 'as big as a barn' compared to what they expected. Later units include 'outhouse' (10⁻⁶ barns) and 'shed' (10⁻²⁴ barns).
Common Mistakes
Thinking a barn is a large area — at the human scale 10⁻²⁸ m² is incomprehensibly small.
Educational Tips
Cross-section = probability of interaction. A bigger barn value means a particle is more likely to 'hit the target' — hence the barn analogy.
About Square Millimeter (mm²)
Definition
The square millimeter is a metric unit of area equal to 10⁻⁶ square meters, or the area of a square 1 mm on each side.
Mathematical Relationship
1 mm² = 0.01 cm² = 10⁻⁶ m². There are 1,000,000 mm² in 1 m².
Conversion Formula
To convert mm² to cm²: divide by 100. To in²: multiply by 0.00155.
Practical Applications
Wire gauge cross-sections, solder pad sizes on PCBs, precision machined surface areas, and needle gauges.
Interesting Facts
A standard 14 AWG electrical wire has a cross-section of about 2.08 mm². The period at the end of this sentence covers about 0.25 mm².
Common Mistakes
Confusing mm² with mm — wire is specified by cross-sectional area (mm²), not diameter. A 2.5 mm² wire has ~1.78 mm diameter.
Educational Tips
In Europe, electrical wire is sized by mm² (cross-section area). The US uses AWG gauge numbers instead.