Count the meals and portions
Start with the dinners you will actually cook and the number of people eating each one. Keep the recipe quantity separate from the amount sold in a packet. If two meals both need an ingredient, total the needed amount before deciding how many packs to buy.
Subtract what you already own
Check the cupboard, fridge and freezer, including dates and usable amounts. Cross off ingredients you already have only when they are suitable for the meal. Keep optional extras separate from essentials so you can adjust the shop.
Check the real basket
Choose your supermarket, location and fulfilment method. Compare actual pack sizes, shelf or online prices, loyalty conditions and any delivery charge before ordering. The cost of whole packs paid at checkout differs from the cost of ingredients used in a meal. Do not count a leftover as a saving unless you really use it later.