For a documented replacement, start with the original batch total, subtract the old ingredient’s contribution and add the new one’s. Changing a name in the recipe without changing the numbers leaves the original ingredient in the calculation.
Update an invented batch
Suppose a fictional batch totals 1,500 calories and 75 g protein. Its original ingredient contributes 300 calories and 10 g protein. The replacement, at the actual included amount, contributes 220 calories and 18 g protein. The new batch is 1,420 calories and 83 g protein.
Recompute the portion
If it is still divided into five uniform portions, each has 284 calories and 16.6 g protein. If the replacement changes the total cooked weight, an old per-gram density no longer applies. Use the new measured batch mass for weight-based portions.
A substitution needs evidence
The replacement’s nutrition must come from its own matching label or database entry. Equal ingredient weights do not imply equal nutrients. A restaurant substitution also needs official support; this method does not certify that the restaurant offers it or that a generic ingredient profile matches it.
FDA’s serving explanation and USDA’s food-identity documentation support the inputs. The values here are invented. The calculation is an original worked example, not a tested recipe. Record the original component, replacement amount and source basis so another person can audit precisely what changed.
Sources and example boundaries
- FDA: serving information
Serving sizes and household/metric units on U.S. labels.
- USDA: Foundation Foods documentation
Food descriptions, portions, missing nutrients and sample variation.
All food figures and prices in the worked example are invented to explain the method. They are not restaurant nutrition, tested recipes, shopping prices or personal dietary advice. Use the current label for the product you actually have.