Barn to Square Millimeter Converter

Area Converter

20 units available

Decimals:

From

To

1.000000e-22

1 b = 1.000000e-22 mm²

Formula:

mm² = b × 1.000000e-22

With your value: 1 b = 1.000000e-22 mm²

How big is that?

Everyday references on a logarithmic scale, all expressed in barn so you can sanity-check the result.

Your value1.00 b

Postage stamp (6.0e+24× your value)6.00e+24 b

A4 sheet (6.2e+26× your value)6.25e+26 b

Parking space (1.3e+29× your value)1.25e+29 b

Tennis court (2.6e+30× your value)2.61e+30 b

Football pitch (7.1e+31× your value)7.14e+31 b

Other Barn to Square Millimeter conversions

2 b to mm² 3 b to mm² 4 b to mm² 5 b to mm² 6 b to mm² 7 b to mm² 8 b to mm²

Barn to Square Millimeter Conversion Table

Barn (b)	Square Millimeter (mm²)
0.5	5.000000e-23
1	1.000000e-22
2	2.000000e-22
5	5.000000e-22
10	1.000000e-21
15	1.500000e-21
20	2.000000e-21
25	2.500000e-21
50	5.000000e-21
100	1.000000e-20
250	2.500000e-20
500	5.000000e-20
1000	1.000000e-19

Square Millimeter to Barn Conversion Table

Square Millimeter (mm²)	Barn (b)
0.5	5.000000e+21
1	1.000000e+22
2	2.000000e+22
5	5.000000e+22
10	1.000000e+23
15	1.500000e+23
20	2.000000e+23
25	2.500000e+23
50	5.000000e+23
100	1.000000e+24
250	2.500000e+24
500	5.000000e+24
1000	1.000000e+25

Where these values come from

Every factor on this page is traced to the document that defines it. See the full provenance dataset or our methodology.

Barn (b)

Area

Exact conversion

Derived from the square metre via the length definitions above.

Source: NIST Special Publication 811, Guide for the Use of the International System of Units

National Institute of Standards and Technology (US) · Reviewed 2026-07-01

Square Millimeter (mm²)

Area

Exact conversion

Derived from the square metre via the length definitions above.

Source: NIST Special Publication 811, Guide for the Use of the International System of Units

National Institute of Standards and Technology (US) · Reviewed 2026-07-01

How to Convert Barn to Square Millimeter

To convert from Barn (b) to Square Millimeter (mm²), multiply the value by 1.000000e-22.

Formula: mm² = b × 1.000000e-22

Reverse: b = mm² × 1.000000e+22

Step-by-Step Example

Start with your value in Barn. For example: 5 b
Multiply by the conversion factor: 5 x 1.000000e-22
The result is: 5.000000e-22 mm²

About Barn

The barn (b) is a unit of area. One barn equals 1.000000 × 10^-28 square metres. UnitConvertLab converts it against every other area unit using this exact definition, so results are reproducible to full double precision rather than rounded lookup tables.

Common uses: area calculations, engineering and science, education.

About Square Millimeter

The square millimeter (mm²) is a unit of area. One square millimeter equals 1.000000 × 10^-6 square metres. UnitConvertLab converts it against every other area unit using this exact definition, so results are reproducible to full double precision rather than rounded lookup tables.

Common uses: area calculations, engineering and science, education.

Frequently Asked Questions

How many Square Millimeter are in 1 Barn?

There are exactly 1.000000e-22 Square Millimeter in 1 Barn. This means the conversion factor from Barn to Square Millimeter is 1.000000e-22.

What is the formula to convert Barn to Square Millimeter?

The formula to convert Barn to Square Millimeter is: mm² = b × 1.000000e-22. For example, to convert 10 Barn to Square Millimeter, you would multiply 10 by 1.000000e-22.

What is a Barn?