Define the comparison before doing the maths
Write down the exact products, pack versions, stated purpose, species and life stage. Decide whether you are comparing a printed label field, a dry-matter proportion, an amount per calorie or a cost measure.
Do not mix guaranteed minima, typical analyses and laboratory results without labelling the difference. They are different kinds of observations even when the units look identical.
Use dry matter only when moisture is supplied
Dry matter is 100 minus the moisture percentage. Divide the as-fed nutrient percentage by the dry-matter percentage, then multiply by 100. Apply the same calculation to both products.
If one label omits moisture, the dry-matter comparison is unavailable. An assumed moisture value may be useful in a private scenario analysis, but it is not a source-backed product fact and should never be published as one.
Use an energy basis only when kcal is comparable
To express grams per 1,000 kcal from a percentage and kcal per 100g, divide grams per 100g by kcal per 100g and multiply by 1,000. Keep the manufacturer energy method or source note if available.
Per-calorie values describe concentration relative to energy. They do not by themselves establish digestibility, bioavailability, nutritional adequacy or an appropriate feeding amount.
- Same nutrient definition
- Same unit basis
- Moisture supplied for dry matter
- Energy supplied for per-calorie view
Record the result as evidence, not a verdict
Show inputs, formula, output and missing fields together. A reader should be able to reproduce the number and see which decisions the data cannot support.
A larger or smaller value is not automatically better. Use the comparison to frame a more precise question, and take animal-specific or clinical questions to a qualified professional.