Meal prep fails in the shop, not in the kitchen. People cook a big batch on Sunday with no plan for quantities, then run out of chicken by Wednesday or throw away a tray of rice on Friday. A portion planner fixes the shopping list before the cooking starts: enter how many people you feed, how many days you prep for, and the grams of protein, carbs, and vegetables each person eats per day, and it totals the whole week in kilograms. You shop once, cook once, and the food lasts exactly as long as planned.
The maths is multiplication, but doing it by hand for three food groups across five days invites errors. With four people, five days, and 150 grams of protein per person per day, the total is 4 times 5 times 150, which is 3,000 grams, or 3 kilograms of protein foods. Carbs at 200 grams give 4 kilograms, and vegetables at 250 grams give 5 kilograms, for a total of 12 kilograms of food. Seeing the total in kilograms is what makes the shopping list real: it tells you whether two shopping bags will do, or whether you need the car.
Here is a worked example for a smaller household. Two people prepping for five days, with the same daily portions, need 2 times 5 times 150 grams of protein, which is 1,500 grams, plus 2,000 grams of carbs and 2,500 grams of vegetables, totalling 6 kilograms. Split across five days, that is 1.2 kilograms of food per day for the household, or 600 grams per person per day, which matches a normal lunch and dinner with a small breakfast. If your household eats three full cooked meals a day, raise the daily grams rather than stretching the same totals thinner.
Portion grams need a reality check against your own eating. The defaults here, 150 grams of protein, 200 grams of carbs, and 250 grams of vegetables per person per day, suit a moderately active adult eating mostly home-cooked meals. Teenagers, manual workers, and athletes often need more, while small children need far less, roughly half for a young child. Start with the defaults for one week, weigh what is left over, and adjust: leftovers mean the portion was too big, and empty containers by Thursday mean it was too small.
Cooking changes weights, and the planner uses cooked-weight thinking, so shop with a margin. Raw chicken loses about a quarter of its weight as water and fat in cooking, while dry rice roughly triples in weight when cooked. That means 3 kilograms of cooked protein may need close to 4 kilograms of raw meat, while 4 kilograms of cooked carbs may need only about 1.3 kilograms of dry rice or pasta. Buy about 10 percent extra of raw ingredients on the first week, keep notes on what ran out, and your second week list will be close to exact.
Storage and variety turn a plan into food people actually eat. Divide the cooked totals into daily containers on prep day, label them with the day, and refrigerate what you will eat within three days while freezing the rest. Cook two proteins and two carb bases rather than one of each, so the week does not taste like the same plate five times. Sauces and spices are cheap variety: the same chicken and rice becomes a different meal with a tomato sauce one day and a soy and ginger dressing the next.
Food safety sets the real limit on how far ahead you can prep, and it is stricter than most people think. Cooked meals keep safely in the fridge for three to four days, so a five-day plan needs the last two days frozen and thawed overnight in the fridge, not on the counter. Cool cooked food within two hours, store it in shallow containers so it chills fast, and reheat each portion until it is steaming hot all the way through. When in doubt, throw it out: a planned portion that goes bad costs far less than a day of food poisoning, and a freezer is the tool that makes a full-week plan safe.