hectare
haarea · International · Modern
Non-SI unit accepted for use with the SI; 1 ha = 10⁴ m².
Converter
area · Various · Modern
barn
bexact
- Record
- M363
- Definition quality
- Standardized
- Conversion mode
- multiplicative
- Calculator
- Fully calculable
Definition
Barn: exactly 10^-28 m²; a non-SI unit accepted for use with SI by NIST guidance.
Reference value
One barn is equal to 1.000000 × 10^-28 square metres.
History & use
Specialized nuclear/particle-physics cross-sectional area unit.
Modern use
Still used for nuclear and particle interaction cross sections.
Did you know?
Despite the comic-sounding name, the barn is a real scientific unit with an exact SI conversion.
Sources & evidence
Source tier Tier A · confidence High
Related measurements
area · International · Modern
Coherent SI derived unit for area, equal to metre squared.
acre
acrearea · UK / US · Modern / historical
1 acre = 43,560 ft² = exactly 4046.8564224 m² using the international foot.
square foot
ft²area · UK / US · Modern / historical
1 ft² = exactly 0.09290304 m².
square yard
yd²area · UK / US · Modern / historical
1 yd² = exactly 0.83612736 m².
square mile
mi²area · UK / US · Modern / historical
1 mi² = exactly 2,589,988.110336 m².
area · International · Modern
1 km² = exactly 10^6 m².
square inch
in²area · US / UK · Modern
1 in² = exactly 0.00064516 m².