1 hectare =      0.003 861 021 585 5 square mile
1 hectare = 11 959.900 463 square yards
1 hectare = 10 000.000 square meters
1 hectare =      1.1172508764e-28 square light years
1 hectare =      2.471 053 814 7 acres
1 hectare =      1.525 553 013 0 acres [Ireland]
1 hectare =      2.471 043 920 2 acres [survey]
1 hectare =      2.989 975 115 8 acres [suburbs]

Amazing what you can find on the net, ain't it. Of course some of it is more useful than the rest. It was a revelation how many different variants on 'an acre' are used.