How to calculate nutrition per serving

1. Start with the nutrient profile for each ingredient

Most food-composition databases express nutrient values on a standard basis, commonly per 100 g. To calculate the contribution of an ingredient, multiply the nutrient value by the number of grams used and divide by 100.

The food profile should match the ingredient as closely as possible. Raw and cooked foods can have different water content and nutrient values, while branded products may differ materially from a generic equivalent.

2. Add the ingredients to get the recipe total

Repeat the calculation for every ingredient, then sum the values. At this point you have the nutrient total for the complete recipe batch.

This is also where ingredient mapping quality matters most. A mathematically perfect formula cannot correct a poor match between the food used by the kitchen and the nutrition profile selected in the database.

• Use edible quantities where the recipe specification is based on edible weight.
• Check whether oils, sauces, garnishes and other small additions are included.
• Use the same recipe version that the kitchen is actually producing.

3. Record the finished yield

Cooking and preparation can change the weight of the recipe through water loss, water gain, drained liquid, fat gain or fat loss. That means the sum of the starting ingredient weights is not automatically the finished recipe weight.

FAO/INFOODS guidance distinguishes yield factors, which describe weight change, from nutrient retention factors, which describe nutrient retention after preparation. Measuring final yield is therefore an important operational step rather than a substitute for nutrient-retention logic.

4. Define the portion

If the recipe produces a known number of portions, divide the recipe nutrient total by that number. If the kitchen serves a fixed gram weight, the portion count can be derived from the measured final yield.

• Example: a 2,400 g finished recipe served as 12 equal portions gives a 200 g serving weight.
• If the final yield changes, the per-100 g value may change even when the ingredient list stays the same.
• If the number or weight of portions changes, the per-serving result changes.

5. Review the result before publishing

A recipe calculation should be reviewable. Keep the ingredient source, quantity, food match, final yield, portion count and any retention assumptions with the calculation.

For restaurants and hotels, this is especially important when a recipe changes, a supplier changes, or a menu item is resized. The nutrition result should be updated from the same controlled recipe rather than copied forward from an old spreadsheet.