It’s possible for a person to grow all their (approximately 322 Lbs.)vegetarian food in 200 sq. ft growing area with a 6 month growing period.
Plant that same area with winter wheat and/or winter rye, and you will have enough to make a loaf of bread every week and a half.
Increase that area to 300 sq. ft. and you’ll be able to have a loaf of bread every week, and about 160 lbs of extra produce to share with a neighbor, or sell at the farmers market.
I haven’t measured the square footage of the planters I use but I’m sure it isn’t more than 50 square feet. Still, I get enough for myself and maybe a neighbor or two.