Calories per serving calculator
Only as accurate as the ingredient figures you started from. Cooking losses, absorbed oil and drained liquid all shift the real total.
Calories per serving is the recipe total divided by the number of servings. A 2,400 kcal dish serving six is 400 a portion, and if the finished dish weighs 1,800 g, that is 133 kcal per 100 g and a 300 g serving.
How to work out calories per serving
The division here takes a second; the total you feed it is where all the difficulty lives. Every figure in every food database comes from the same small set of conversion factors, set out in European labelling law and originating with Atwater over a century ago: four kilocalories per gram of protein, four per gram of carbohydrate, nine per gram of fat, seven per gram of alcohol and two per gram of fibre. Fat carrying more than twice what protein and carbohydrate do is why cooking oil is the single most under-counted ingredient in home calorie sums. A tablespoon of it is around 120 kcal, and three tablespoons across a family dish is a serving’s worth on its own.
Cooking does not create or destroy energy, but it moves weight around, and the panel is built on that distinction. Sum the raw ingredients and you have the total energy of the dish; weigh it after cooking and you have the mass you will actually eat. Divide one by the other and the per-100-gram figure is correct even though the dish lost water on the way, which is exactly why the weight field asks for the cooked weight. A kilogram of chicken that loses a quarter of its weight as water still holds the same calories in 750 grams, so its density rises by a third while its total does not move at all. The one thing that does change the total is anything you pour away: drained fat, discarded poaching liquid and pasta water all leave with some energy in them.
Per 100 grams is the figure to keep, because a serving is a decision and a gram is not. A dish that serves six generously serves four properly, and nobody argues about the weight of what is on their plate. European labelling requires energy to be declared per 100 g or per 100 ml for the same reason, so a home-cooked figure on that basis sits directly alongside anything from a supermarket. What none of this survives is precision claims: ingredient databases disagree with each other by around ten per cent, produce varies naturally, and dividing a pot by eye adds more error than the arithmetic ever will.
What people use it for
- Logging a home-cooked meal against a food diary
- Batch cooking with portions that are actually consistent
- Comparing a recipe against a ready meal on the same basis
- Working out what a second helping really costs
- Getting a per-100-gram figure for something you cook often
Questions
Add the calories of every raw ingredient, then divide by servings. Include the cooking oil, which is where most home estimates go wrong.
From conversion factors applied to the protein, fat, carbohydrate, fibre and alcohol content: 4 kcal per gram for protein and carbohydrate, 9 for fat, 7 for alcohol and 2 for fibre.
Raw for the calorie total, cooked for the weight. That combination is what makes the per-100-gram figure describe what you are actually eating.
Not the energy. It changes the weight, so water loss concentrates the calories per gram without altering the total. What does change the total is anything drained away.
Count what ends up in the food. Frying absorbs a real share of it, roasting on a rack lets most of it drip clear, and a tablespoon is about 120 kcal either way.
Because serving size is a judgement and weight is not, and because it matches how packaged food is labelled. It is the only basis on which a home-cooked dish and a ready meal can be compared at all.
No, and nothing that starts from an ingredient database can be. Expect around ten per cent from the data alone before you add whatever portioning by eye contributes. It is a good estimate and it should be used as one.