That “one year supply” thing always bugged me too—everyone eats differently, and needs change with age and health. What’s worked for me is starting with calorie requirements: average adult needs about 2,000 calories a day, but kids, teens, and folks with medical issues will need more or less. I made a spreadsheet with everyone in the house, factoring in higher calories for more physical work (digging, hauling water, etc). Then I listed main staples (rice, beans, oats, etc) and figured out how many calories per cup for each.
For dietary restrictions, I use a separate column, so I know not to store stuff my husband can’t have (he’s diabetic, so less sugar,