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Calories In Food Portion Calculator

Work out calories in food portion instantly with clear inputs, formula shown and shareable results.

About Calories In Food Portion Calculator

Scales the per-100-gram energy figure on the label to the portion actually eaten and expresses it against a daily target.

Formula

Portion energy

Portion calories = calories per 100 g x portion grams / 100

Worked example

With the default values below, Calories In Food Portion Calculator returns Calories in the portion of 375.0. Change any input above and every figure here is recalculated in your browser.

Inputs used

Calories per 100 gaccepts 1–900 kcal
250 kcal
Portion sizeaccepts 1–3,000 g
150 g
Daily energy targetaccepts 800–6,000 kcal
2,000 kcal

Results

Calories in the portion
375.0 kcal
Share of the daily target
18.75%
Calorie density
2.500 kcal/g
Grams providing 100 kcal
40.0 g

Step by step

  1. 1Values used
  2. 2Portion energy
  3. 3Calories in the portion= 375.0 kcal
  4. 4Share of the daily target= 18.75
  5. 5Calorie density= 2.500 kcal/g
  6. 6Grams providing 100 kcal= 40.0 g

Assumptions and limits

  • The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.
  • This is an estimate for general information and not professional medical advice. See the full disclaimer for the limits that apply to this kind of calculator.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.

Frequently Asked Questions

Why do labels use 100 g?

It allows direct comparison between products regardless of pack size, which per-serving figures obscure.

Are label values exact?

They are averages with legal tolerances of up to 20%, and cooking changes them further.

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