It depends on the units for 30x28.
Is it 30 ft x 28 ft
or 30 inches x 28 inches
or 30 miles x 28 miles?
if you have a square acre how many ft. across is it
18-ft x 11-ft = 198 square ft
221 square feet
960 square feet.
There are 324 square feet
100-ft x 200-ft = 20,000 square feet
11 * 16 = 176 square feet
87.75 square inches
1750
180 square feet.
87120 square ft. in 2 acres.
414 square feet