Use this tool when food-composition values are already available and you need a deterministic, reusable calculation. It works well in a tool chain, an application backend, a recipe workflow, or a test fixture where the exact input records and reference values must be explicit. Use the interactive Nutrition Calculator instead when a person needs to search tool.io's normalized USDA dataset and choose foods visually.

• Total calories, macronutrients, vitamins, or minerals across several weighed foods.
• Calculate a recipe or meal from normalized per-100-gram composition records.
• Keep separate servings of the same food distinguishable through selection IDs.
• Compare calculated totals with a caller-supplied reference profile.
• Detect totals that are incomplete because one or more selected foods omit a nutrient.

Nutrient identity

A stable ID such as nutrient.protein. Values are combined by identity, not by a possibly ambiguous display label.

Amount per 100 grams

The normalized composition amount used as the common basis for scaling each food to its entered weight.

Selection ID

An optional identifier for one occurrence of a food, allowing two portions of the same food record to remain separate in the contribution breakdown.

Reference profile

A caller-defined collection of comparison values. The tool does not silently choose a jurisdiction, age group, or medical target.

FoodData Central is one suitable source for normalized food composition, but its records represent specific foods, preparations, and data types. Retaining the source record identifier outside this calculation makes results easier to audit and reproduce.^{[3, 4]}

For every food and nutrient, the calculation multiplies the amount reported per 100 grams by the selected food weight divided by 100. Contributions with the same nutrient ID are converted within compatible unit families and summed. Grams, milligrams, and micrograms can be reconciled as mass; kilocalories and kilojoules can be reconciled as energy. A mass value is never combined with an energy value.

A nutrient is marked complete only when every selected food reports that nutrient. When one food omits it, the known contributions are still added, but complete is false. This prevents an absent database field from being represented as a measured zero.

If a compatible reference exists, the percentage is the total divided by the reference amount and multiplied by 100. For a range, the output can report the percentage of both its lower and upper amounts. The comparison label is preserved so a user interface can distinguish a target from a maximum or minimum.

The arithmetic can be exact while the dietary estimate remains uncertain. Food composition changes with cultivar, formulation, preparation, cooking, drainage, storage, and laboratory method. This tool does not inspect the provenance or freshness of supplied nutrient values and cannot determine whether a food record matches what was eaten.

• It does not search, identify, or disambiguate foods.
• It does not estimate edible yield, cooking loss, nutrient retention, or moisture change.
• It does not infer missing nutrients and never assumes that an omitted value is zero.
• It does not model bioavailability, interactions between nutrients, or absorption differences.
• It accepts only the documented mass and energy units; unsupported or inconsistent units are rejected.
• It does not create a personalized reference profile from age, sex, body size, pregnancy, activity, or medical history.

Recommended Dietary Allowances, Adequate Intakes, Estimated Average Requirements, Tolerable Upper Intake Levels, and label Daily Values have different meanings. NIH guidance emphasizes that individual requirements may differ from population reference values, so the percentage output should not be used to diagnose a deficiency or prescribe supplements.

Use the interactive calculator when a person needs food search, record labels, weights, and visual nutrient groups. Use Macronutrient Split when the task is to convert calorie percentages into gram targets rather than total actual foods. Use Compare Food when the purpose is to inspect equal-weight facts for several foods side by side.

• Interactive Nutrition Calculator

  Search normalized USDA food records, add portions by weight, and inspect the calculated nutrient table.

• Compare Food

  Compare catalog foods on a common per-100-gram basis without assembling a meal.

For branded packaged foods, compare the calculation with the current Nutrition Facts label for that exact product. The FDA explains that percent Daily Value describes how much a nutrient in one labeled serving contributes to a daily diet.

• Macronutrient Split

  Convert a calorie target and carbohydrate, protein, and fat percentages into daily gram targets.

• Compare Anything

  Align structured facts for foods, products, and other catalog items in side-by-side columns.

• Body Mass Index

  Calculate a height-to-weight screening ratio; BMI does not measure food intake or nutrient adequacy.