There are 43,560 square feet in one acre of land.
If you have a half of an acre of land then you would have 21,825 square feet in the half of an acre.
Most suburban lots or town lots are half an acre or less in size however some people may own a full acre of land in the town.
My town lot is half an acre so it would be 21,825 square feet.
Some lots in suburban or towns can also be as small as one-quarter and one-fifth of an acre and the houses especially new houses take up most of the land so there is usually more indoor space than there is outdoor space.