Portion Size Calculator
Convert nutrition labels into real-world portions — or work backwards from a calorie budget to the grams you can serve.
kcal per 100 g
250
Calories in portion
375 kcal
Formula
calories per portion = total calories ÷ total grams × portion gramsHow to use the Portion Size Calculator
- 1Enter the calories and weight per serving from the label
- 2Enter your portion size in grams (or target calories)
- 3Read the calories in your actual portion
Frequently Asked Questions
Why do labels mislead on portions?
Manufacturers sometimes list unrealistically small serving sizes (e.g. half a muffin) to lower the printed calorie number. Always check grams.
How do I measure portions without a scale?
Handy references: a palm ≈ 100–120 g protein, a cupped hand ≈ ½ cup carbs, a thumb ≈ 1 tbsp fat.