Mindful nutrition tool
Serving Size & Calorie Calculator
Calculate calories, protein, carbs, fat, and fiber for the amount you ate. Convert nutrition per 100 g, per 100 mL, or per labeled serving without signup.
A calmer way to startFrom the label to your plate
Entries stay in this page and clear on reload. Changing units clears weights so they cannot be mistaken for converted values.
Make your portion make sense.
Enter your label values and amount eaten to see your portion’s nutrition.
Calculate nutrition for the portion you ate
Multiply each nutrition-label value by the amount eaten divided by the amount that value describes. For example, 240 kcal per 100 g becomes 156 kcal for 65 g: 240 × 65 ÷ 100.
Choose per 100 g/mL or per serving, enter your portion, and copy the calorie and nutrient values from the label. You can enter just calories, just protein, or any combination. Blank values remain not entered; they are not silently counted as zero.
Formula and units
Portion nutrient = label nutrient × (amount eaten ÷ label amount)
Use grams with grams, or milliliters with milliliters. Do not mix mass and volume: 100 mL does not necessarily weigh 100 g. Changing the unit clears amounts to avoid reinterpreting an existing weight as a volume. Nutrition values remain as entered, so check that they describe the new basis.
Calculations use full precision and display up to two decimal places. Printed labels are already rounded, so extra displayed digits do not make the underlying nutrition exact. This is a portion-scaling tool, not a laboratory analysis or a commercial nutrition-label generator.
Worked examples
| Label says | Amount eaten | Calculation | Portion calories |
|---|---|---|---|
| 240 kcal per 100 g | 65 g | 240 × 65 ÷ 100 | 156 kcal |
| 180 kcal per 40 g serving | 60 g | 180 × 60 ÷ 40 | 270 kcal |
| 50 kcal per 100 mL | 250 mL | 50 × 250 ÷ 100 | 125 kcal |
For the first example, if the same label lists 10 g protein, 30 g carbs, 9 g fat, and 4 g fiber per 100 g, the 65 g portion contains 6.5 g protein, 19.5 g carbs, 5.85 g fat, and 2.6 g fiber by proportional scaling. The figures are illustrative label values.
Why use the label’s calories?
We scale the energy printed on the label directly. We do not overwrite it by recalculating energy from rounded macro grams. Label rounding and how ingredients such as fiber are treated can produce differences. If the package provides only kilojoules, convert to kcal before entering its Calories field: kcal = kJ ÷ 4.184.
The FDA guide to reading Nutrition Facts labels explains how serving size relates to listed calories and nutrients. A labeled serving is not a personalized recommendation for how much to eat.
For logging tips, see how to read a nutrition label. If you weighed food after cooking but your entry is for uncooked food, visit the Raw & Cooked Weight Converter and review its limitations.
Serving-size calculator questions
How do I convert calories per 100 g to my serving?
Multiply calories per 100 g by your portion in grams, then divide by 100. Enter those same values in the calculator to scale any other nutrients you know.
Can I calculate more than one serving?
Yes. Enter the total amount you ate. If one serving is 40 g and you ate 80 g, the calculator doubles the entered nutrition values. Fractional servings work the same way.
What if I only know calories?
Enter calories and leave other fields blank. The result will show calories and mark those other nutrients as not entered. Entering zero specifically means the label lists zero.
Does it calculate a daily calorie target?
No. This tool scales food-label values for a portion. Use the Calorie & Macro Calculator for an estimated daily target.
Are my entries saved or sent to analytics?
No entries are saved by this tool or included in analytics. They remain in the page’s browser state until reload. “Copy your plan” copies the summary only when you request it.
For a dish with several ingredients, use the Recipe Nutrition Calculator to add ingredient nutrition and divide the whole recipe into servings.