Cooking Losses and Calories: Water, Fat and Final Weight

Updated 17 October 2026 · Reviewed by Tools by Layna Editorial Team · General information only

A recipe can become lighter without losing energy in the same proportion. To interpret cooking losses, identify what left the food: water, nutrient-containing material, or both. A percentage change in weight cannot answer that by itself.

Evaporation changes concentration

Imagine a stew starts at 2,000 g with an estimated 2,000 kcal. After simmering, it weighs 1,500 g. If the only loss is water, the batch still contains approximately 2,000 kcal. Its density rises from 100 to about 133 kcal per 100 g.

A 25% loss of weight would therefore not justify subtracting 25% of the calories. FSANZ notes that much cooking-weight change comes from water, although fat can also be gained or lost. Real cooking should be assessed against the ingredients and discarded material.

Absorbed water works in the opposite direction

Suppose a hypothetical amount of dry rice contains 700 kcal and weighs 200 g. After absorbing water it weighs 600 g. If nothing with energy was added or discarded, the cooked batch remains approximately 700 kcal: about 117 kcal per 100 g.

The added 400 g is not an extra ingredient containing 400 g of carbohydrate. This is why raw and cooked food-database entries cannot be swapped while keeping the same weight. Match the preparation state used in the measurement.

Rendered fat is not the same as evaporated water

If fat is discarded, some energy leaves the edible batch. However, liquid poured from a pan can contain water, fat and other material. Its weight alone does not reveal its energy content. Do not deduct 9 kcal for every gram of mixed cooking juice.

For scale only, 10 g of pure fat would represent about 90 kcal using the usual approximate fat-energy factor. That is a composition example, not a method for analysing pan drippings. Use a suitably matched cooked-and-drained food entry when available, or clearly record the uncertainty.

Choose one coherent estimation method

One approach is to total the measured raw ingredients and then account for meaningful discarded ingredients, using final yield for portions. Another is to use an appropriate cooked-food entry for the actual cooked amount. Mixing the raw total with an additional cooked-meat entry counts the same food twice.

Keep added oil visible. If you cannot establish how much remains in the food, record that limitation rather than presenting a precise deduction from the pan’s appearance.

Apply the final weight to portions

Once an edible-batch energy estimate is chosen, divide it by the final edible weight to estimate energy per gram. The portion-size guide works through this step. The recipe calculator only divides an entered total into equal servings; it does not estimate evaporation or fat retention.