Per 100 g to Serving Calculator
Turn a nutrition label's per-100 g figures into what a serving of any size contains — energy, protein, fat, carbohydrate, sugar and sodium — with the serving's share of a daily energy figure and the servings in the pack.
Labels give nutrients per 100 g so that products can be compared; what you eat is a serving, which is rarely 100 g.
How the per 100 g to serving calculator works
Labels give nutrients per 100 g so that products can be compared; what you eat is a serving, which is rarely 100 g. Multiply each figure by the serving weight over 100 and you have the serving's content. Against a daily energy figure — 8,700 kJ or 2,000 kcal is the usual reference — the serving's share of a day appears, which is the number that makes a snack comparable with a meal.
Formula: per serving = per 100 g × serving weight / 100; share of day = serving energy / daily energy
Worked examples
| Inputs | Energy per serving | Note |
|---|---|---|
| A 45 g serving of cereal | 743 kcal | under a tenth of the day |
| Eating the whole pack | 4950 kcal | over half the day |
| A small serving | 330 kcal | a snack |
FAQFrequently asked questions
Why do labels show per 100 g?
So that products can be compared regardless of pack or serving size. The per-serving column, where it exists, uses the maker's serving — often smaller than what people eat.
What daily energy figure should I use?
The label reference is 8,700 kJ in Australia and 2,000 kcal in Britain and the United States — an average adult. Your own needs may be well above or below it.
How do I convert kJ to kcal?
Divide by 4.184. A 2,000 kcal day is about 8,400 kJ; the Australian 8,700 kJ reference is 2,080 kcal.
What does "of which sugars" mean?
The part of the carbohydrate that is sugar — natural and added together. Labels rarely separate added sugar, so the share of carbohydrate is the best clue.
Is sodium the same as salt?
No: salt is sodium chloride, and sodium is 40% of it by weight. Multiply sodium in milligrams by 2.5 for milligrams of salt.
Where these figures come from
- US FDA — Safe Minimum Internal Temperatures — the internal temperatures the roasting calculator targets
- NIST SP 811 — Guide for the Use of the International System of Units — the exact weight and volume conversions used throughout
- UK Food Standards Agency — food safety and labelling standards
Last checked: September 2026. Baking ratios follow standard baker's percentage practice; roasting guidance follows published safe internal temperatures.