We have 7 in our family and I typically plant about 40 pounds which brings back a yield of 400 pounds typically. Our family eats on the white potatoes most of the summer into early fall then we harvest our sweet potatoes which gives us an additional large harvest to make it through the winter. We typically get 10 pounds return for every 1 pound we plant. Not sure what your return will be so you could use 10 pounds as a starting point then figure out how many pounds you need at harvest time. Then I would over plant by 10 or 20% to make sure you get the number. Hope this helps and happy planting!