The total cost for a concrete garage floor, including concrete, labor, supplies and equipment, varies region to region because of geographic variables. The total cost for a 400-square-foot garage floor in San Francisco ranges between $3.91 and $4.28 per square foot and between $3.26 and $3.60 per square foot in Atlanta.In suburban Chicago, the same floor will cost between $3.70 and $4.05 per square foot.he total cost for a 400-square-foot garage floor in San Francisco ranges between $3.91 and $4.28 per square foot and between $3.26 and $3.60 per square foot in Atlanta. In suburban Chicago, the same floor will cost between $3.70 and $4.05 per square foot.