How many feet make 340 square foot?

Depends. Measuring in feet gives you a single dimension, length OR width. Combining BOTH dimensions then gives you square feet. A patio that is 10 foot wide and 34 feet long would be 340 square feet. 10 X 34 = 340. But then a patio that is 6.8 foot wide and 50 foot long would also be 340 square feet. Hope that helps. If not please re-ask your question a bit differently.