Details are shown in Chart 1 below. As you can see from Chart 1, the estimated average monthly food cost for family of 4 ranges from about six hundred forty-eight dollars ($648) per month on a thrifty plan to around twelve hundred eighty-eight dollars ($1,288) per month on a liberal plan.or all categories combined, the average monthly food cost for a family of 4 in the US is approximately nine hundred sixty-three dollars ($963.00) per month. Question: What is the average monthly food cost for family of 4?