How Many Acres Are in a City Block?

An acre measures 208 feet by 208 feet, or 43,560 square feet, but city blocks vary in size depending on the size and age of the city. In New York City, most city blocks are 660 feet by 330 feet, which is equal to 5 acres. Urban planning, however, has evolved over time, and ideas about the ideal size of city blocks has evolved with it. In some cities, block plots are much smaller. City blocks in Portland, Ore., for example, measure 290 feet by 290 feet, which is just under 2 acres.