The formula
amount = grams per serving × people × times a week
Where it comes from
Planning a shop nearly always fails the same way: you think in meals and you buy in kilos, and between the two there is a multiplication nobody does. The amount of each food comes from three numbers — what goes in one serving, how many of you there are and how many times a week you eat it — and not from a hunch. The unplanned-meals figure is the check: if the plan calls for twenty-eight meals and the list covers ten, there are decisions still to make.
How to work it out by hand
- Count the meals in the plan: people times days times meals a day
- Note for each food the grams that go in one serving
- Multiply by the people and by the times a week it gets eaten
- Multiply the kilos by the price per kilo for the cost
What is worth knowing
Standard servings per person are a starting point: 80 g of dry pasta or rice, 150 of meat or fish, 200 of vegetables, 60 of dry pulses and 100 of bread. Those are average adult amounts; a teenager eats considerably more and a small child about half. Cost per meal is the figure that compares: above two and a half there is room to come down by swapping expensive protein for pulses, and below one there is usually vegetables or fruit missing from the plan.