Portion calorie calculator
Calorie and macro calculator for your portion
Your portion may be different from the serving on the packet. Enter the label values and both weights to calculate what is in the amount you eat. This free calculator works without signing in.
Calculate your portion
Enter the calories from your label and the weight you will eat. Add protein, fat and carbohydrate if you want those totals too. No account needed.
The calculator does not save a meal. To keep a food diary, open FoodWarz and add the food and portion there.
Last updated: October 7, 2026
Start with the right column on the label
If the nutrition values are per 100 g, select that option. If they are for one serving or the whole package, enter the weight that belongs to those values. Choose Calories only for a quick energy calculation, or add protein, fat and carbohydrate from the same label column in the full mode.
- US labels commonly show values per serving. Check the serving weight and servings per container.
- UK labels commonly show values per 100 g or 100 ml, sometimes with a separate portion column. This calculator uses weight, so do not enter millilitres as grams.
- Choose kcal for calories or kJ for kilojoules. Protein, fat and carbohydrate are entered in grams in either case.
How the portion calculation works
Each label value is multiplied by your portion weight and divided by the reference weight. With 200 kcal per 100 g, a 150 g portion contains 300 kcal. With 160 kcal per 40 g serving, a 60 g portion contains 240 kcal. These are arithmetic examples, not a recommendation for how much to eat.
The tool converts ounces of weight to grams before calculating. It converts kilojoules to kilocalories using 1 kcal = 4.184 kJ. Label calories are scaled independently of macros, so the tool does not replace the printed energy value with a protein/fat/carbohydrate formula.
Keep dry and cooked weights separate
A cooked portion can weigh more or less than the original ingredients because of water loss or absorption. Use nutrition values and a weight for the same food state. There is no universal dry-to-cooked conversion that fits every recipe.
Oil, sauces and toppings are not added automatically. If they are not included in the values you enter, record them separately in your diary.
This calculates food portions, not daily calorie needs
This page does not calculate BMR, TDEE, a weight-loss target or a complete recipe from ingredients. It answers one question: how many calories and macros are in a measured amount of food, given the nutrition values you provide.
How to read the label
From one calculation to a food diary
Review before saving
Check the food, portion and macros before adding a meal. An AI estimate is a draft until you confirm it.
Choose your input
Use a photo, text, voice or barcode in the app. You can also choose food from the catalogue or enter it yourself.
Keep a daily record
See saved meals alongside water, weight and habits. Pets, streaks and teams add a playful reason to return.
Portion calculator questions
How do I calculate calories from grams?
Multiply the label calories by your portion weight, then divide by the weight for those label values. For example, 250 kcal per 100 g becomes 375 kcal for 150 g.
Can I use a US Nutrition Facts label?
Yes. Choose per serving or package, enter that serving or package weight and copy the values from the matching label column. Then enter your own portion weight.
Can I calculate a portion in ounces?
Yes. The weight inputs support grams and ounces. These are ounces of weight, not fluid ounces. Cups and other volume measures require food-specific weight information.
Do I need to sign up or upload my label?
No. Enter the values directly and calculate on this page. The calculator does not upload your label or create a diary entry.
Can the calculator find missing nutrition values?
No. Calories only mode needs the energy and weights, so you can calculate without macros. Full mode needs protein, fat and carbohydrate too. Missing values are never treated as zero or estimated automatically.
Look up a food before calculating
Nutrition values are estimates for calorie tracking and may vary by recipe, brand, cooking method and portion size. Not medical advice. Nutrition data methodology