There are slightly less than 2.5 acres in a hectare. The actual figure is 2.47105 acres per hectare. Based on the size of an acre being equal to a square whose sides are 208.71 feet long, the size of a hectare can be compared to a square whose sides are each 515.75 feet, or about 172 yards, in length.
The hectare is not officially included in the International System of Units, or SI, metric system. A hectare, in metric terms, is equal to 10,000 square meters, or 104 m2. The status of the hectare is that of a "non-SI unit" that is accepted for use with SI units, and it is also considered a unit whose use is "expected to continue indefinitely," as noted in Section 4.1 of the SI literature. Trafalgar Square in London, England represents an area of about 1 hectare.