How do you calculate meal prep quantities?

1. Count the meals to prepare, not just the days

Open your calendar and identify the lunches and dinners you will actually eat at home or take with you. Exclude planned meals out, meals already available in the freezer and those you will cook at the time.

For each meal, note the dish you plan to make and who will eat it. The total gives you the number of portions to prepare, but not their size: people with different needs will not necessarily need the same quantities.

Then assign a recipe to each meal. This gives you the number of portions needed for each recipe, without automatically multiplying everything on your shopping list by the number of days.

References: [1][2][6]

2. Make room for prepped meals within your targets

If you track nutrition targets, start with your daily targets for calories, protein, carbohydrates and fat. These depend on factors including your profile, activity and goal: a universal portion size cannot replace them.

Target available for prepped meals = daily target − intake from other meals and snacks.

Apply this calculation to calories and each macronutrient. Then divide what remains between the relevant meals, according to your routine and appetite. You do not need to allocate exactly the same share to each meal.

This step avoids preparing meal boxes intended to cover your entire day when breakfast, snacks or dinner elsewhere already provide some of what you need.

References: [1][2]

3. Calculate one recipe portion before scaling up

Choose a recipe with known ingredient quantities and a stated number of portions, or use your own recipe with weighed ingredients. For each ingredient, use the values on its label or in an identified food composition table, selecting the correct reference: raw, cooked or drained.

If the values are given per 100 g:

Ingredient contribution = value per 100 g × weight used in grams ÷ 100.

Calculate this for calories and each macro, then add up all the ingredients, including oil, sauces and toppings. Divide the recipe's totals by the number of portions, provided you divide the food evenly.

Compare this portion with the allowance available in your day. Adjust the ingredients if needed, then recalculate: changing one food can affect several macros at once.

Once the portion is suitable, multiply each ingredient quantity by the number of portions of that size you need to prepare.

References: [1][2][3][4][5][8]

4. Keep raw and cooked weight references consistent

Raw and cooked weights are not interchangeable. Cooking changes the amount of water in foods, among other things. Do not apply the nutritional values for dry rice to a weight of cooked rice.

The simplest approach is to record ingredients before cooking, then weigh the finished food to divide it between containers. For equal portions:

Cooked weight per container = total cooked weight of the preparation ÷ number of portions.

For an evenly mixed dish, this lets you divide the recipe's estimated nutritional content between portions. If the components remain separate, portion each one separately: rice, chicken, vegetables and sauce.

Avoid conversion factors assumed to work universally. Use the actual measured yield of your preparation when you need to convert between raw and cooked weights.

References: [3][4][5][8]

5. Example: share ingredients without confusing portion sizes

As an illustrative example, imagine you are planning chicken and rice bowls with courgettes and yoghurt sauce, followed by chicken and courgette wraps with the same sauce. The ingredients overlap, but the quantities per meal need to be calculated separately.

For chicken, the weekly requirement is:

Chicken needed = quantity per bowl × number of bowls + quantity per wrap × number of wraps.

Repeat this addition for the courgettes and yoghurt. Rice is only needed for the bowls; tortillas are only needed for the wraps. Include cooking and seasoning ingredients too.

You can then prepare the shared components together and divide them according to each recipe. The organisational benefit comes from this shared preparation, not from assuming every meal should contain the same portions.

References: [6]

6. Turn recipe requirements into actual purchases

Your list should distinguish the quantities needed for recipes from the products you need to buy. Here is what to check before shopping:

• Put each ingredient on a single line and add up the quantities needed across all recipes.

• Express both your requirements and what you already have in the same units, using the weight reference chosen in step 4.

• Subtract usable stock that is not reserved for another meal: you only need to buy the shortfall.

• Check pack details: net or drained weight, whole or already prepared food, and the number of items per pack. Choose enough packs to cover the shortfall.

• Note any surplus caused by pack sizes and plan to use it in another recipe, rather than automatically adding it to your calculated portions.

References: [3][4][5][6][8]

7. Check your budget using the prices of the products you will buy

The cost of the ingredients you use is not always the amount you pay at the checkout. If a recipe uses part of a pack, you still need to pay for the whole pack when you buy it.

Estimated grocery cost = sum of (number of packs to buy × price per pack) for all products.

Compare this estimate with your budget. If it exceeds your budget, identify the purchases contributing most to the total, then consider a different pack size, something you already have or a suitable recipe substitution. Compare prices using the relevant unit, without assuming a larger pack is always better value.

After a substitution, check the portion's nutritional content again. A cheaper ingredient is not necessarily equivalent gram for gram. The final total still depends on prices and availability when you shop.

References: [3][4][5][6]

8. Label your containers and adjust your next prep session

Label each container with the dish, its preparation date and who it is for if portion sizes differ between people. You can then find the right container without repeating the calculations at mealtime.

This guide does not specify storage times: check these separately using product instructions and official food safety guidance.

After eating, distinguish a portion-size error from a planning error. An unfinished meal or one that felt too small suggests reviewing the quantities for that particular portion. A cancelled meal suggests adjusting the number of meals to prepare instead. Note the adjustment to try during your next session, without changing every recipe at once.

References: [6]

References: [7]