Raw vs cooked weight: why 100 g of chicken is two different numbers

Boil 100 g of dry rice and the kitchen scale reads about 300 g. Pan-fry 100 g of chicken breast and it reads about 80 g. Mostly water has moved, but the "per 100 g" line in a calorie app now describes very different food.

Water moves, nutrients stay

Bognár's tables, a reference for calculating nutrients in cooked dishes, sort cooking into three groups: water goes in (boiling or stewing rice and legumes), water comes out (frying meat, baking bread), or water comes out while fat goes in (deep-frying potatoes, for example) (Bognár, 2002). The USDA measures the result for meat and poultry as a cooking yield, cooked weight divided by raw weight times 100, which captures moisture lost, water absorbed and fat gained or lost (USDA ARS).

Protein, starch and most of the fat stay put: lose water and they pack into fewer grams, absorb it and they spread over more.

How far the scale moves

Approximate illustration based on average factors in the cited tables, not Plate Mate data. Your pot, cooking time, water and cut will give different results.

Bognár notes that the water a grain absorbs grows with the amount of grain, while evaporation depends on the pot, the temperature and the time. Two cooks can turn the same 100 g of rice into noticeably different weights.

What frying does to the protein figure

Say raw breast has 20 g of protein per 100 g (a round number for the sum). Fry 100 g, it shrinks to about 80 g, and the same 20 g of protein now works out at about 25 g per 100 g (20 ÷ 0.80). Illustrative example, not Plate Mate data.

Weigh cooked chicken but log a raw entry, and you undercount protein and calories by about a fifth. Rice errs the other way: log 300 g of boiled rice as dry and you count roughly three times the energy you ate.

Logging it right

1. Weigh and log in the same state. In your app, "rice, white, cooked" and "rice, white, dry" are different foods.
2. Match the method too: frying can add fat, and roasting removes more water than poaching.
3. For batch cooking, add up the raw ingredients, weigh the finished pot and work out your share of it. FAO/INFOODS lists "applying values per 100 g and forgetting to adjust for the actual weight" as a typical error in recipe calculations (FAO/INFOODS).
4. Log the oil in the pan, the sauce and the skin. Leave out bones and peel, which nobody eats.

Consistency beats accuracy to the gram: log the same way every time and your days stay comparable.

A ready meal has done the conversion

Figures on a ready meal describe the finished dish, so you log the pack as one item. The current menu is on our website, with calories and macros per pack for each dish; the assortment varies by machine.

Chicken Fricassee with Buckwheat

500 kcal · P 30 · F 22 · C 50

Per pack. Calculated from the recipe, not measured in a lab.

See the full menu →

Calories and macros on our packs are calculated from the recipe (ingredients and weights), not measured in a laboratory. Weight changes in cooking are one reason such a figure is a guide rather than an exact value for every pack; how recipe nutrition is calculated explains the method and its limits. Next: nutrition per pack explained for meals of different sizes, and comparing protein per portion.