Question: 1 acre means how much hectare?
Answer: An acre is about 0.405 hectare and one hectare contains about 2.47 acres. In 1795, when the metric system was introduced, the are was defined as 100 square metres and the hectare ("hecto-" + "are") was thus 100 ares or ​1⁄100 km2 (10,000 square metres).