MS. Town, an acre is 43,560 sq. ft. or 4,840 sq. yds. A football field, 40 yds. by 100 yds., is 4,000 sq. yds. Now, if it was just laid out in a perfect rectangle, life would be simpler.
The best bet is to take a piece of graph peper and draw it out to whatever scale you choose. Then do the math. It will be a rough approximation because nature seldom works like we think. But, it will be close enough.