A hectare is the European equivalent of an American acre, except it's a lot bigger—10,000 square meters, or 2.471 acres. As in the United States, the unit is used to describe the size of a winery's vineyard. FYI, a hectoliter, which measures a European winery's output, is 100 liters, or 26.47 gallons. Ergo, wine yields are often identified in terms of hectoliters per hectare.