ch²
square chain
Areaexact by definition
A square chain is exactly 404.68564224 square metres, one tenth of an acre. It is the unit that makes surveyor's arithmetic work: measure a parcel in chains, multiply, and divide by ten to get acres with no conversion constant anywhere in the calculation.
| 1 ch² | 404.68564 m² |
Where the unit came from
This is the whole reason Gunter picked 66 feet for the chain. An acre had already been fixed at one furlong by one chain, and ten square chains landing exactly on an acre made the chain the only surveying instrument that decimalised an inconvenient system.
Solvers that use area