Homemade recipe macros: when should you round?
Your calculator shows 18.666666 g of protein per serving. You do not need to copy every digit. Distinguish arithmetic precision from the precision of the underlying information, then use a consistent display.
Detailed results are still estimates
ANSES describes Ciqual as a table of average food composition. A reference value is not an analysis of your particular plate. Extra decimal places do not turn an average into an exact measurement. Keep an estimated-values label even when the arithmetic is careful. The official source is linked below.
Keep decimals until the total
Calculate each ingredient contribution, add them and then divide by servings. Avoid rounding each small contribution first. Fictional example: three contributions of 1.4 g total 4.2 g. Rounding each to 1 g first would give 3 g. If your final display uses whole grams, 4.2 g would appear as about 4 g. These numbers explain the method, not a guide recipe.
Choose a readable serving display
A fictional recipe containing 56 g protein divided into three equivalent servings gives about 18.7 g each with one decimal, or about 19 g as a whole number. Choose a readable convention and apply it consistently. This is a personal worksheet convention, not a commercial labelling rule or a protein intake recommendation.
Reuse saved calculations, not rounded displays
When changing servings, return to saved working values. Multiplying the displayed 19 g by three gives 57 g, whereas the original total was 56 g. That difference comes from rounding. Keep working values for calculations and simplified values for reading; a short note can explain why displayed figures do not always add back exactly.
Check the basics first
Before correcting decimals, check units, quantities, per-100-g versus per-serving references and the food state described. Check that every ingredient is included. A misunderstood column can matter more than final rounding. Related articles cover labels, raw and cooked weights and unequal servings. The Yumlean guide includes recipes with portions and estimated macros to use without assuming excessive precision.