Raw and Cooked Weight

Foundation · 10 min

Weight changes, energy does not

Cooking's main effect is an exchange of water. Grains and legumes absorb water as they boil and get heavier; meat, chicken and fish lose water as they cook and get lighter. The critical point is this: water carries no energy. The energy in 100 grams of raw rice spreads out across roughly 250-300 grams once cooked, but the total stays the same. In other words, a food's total energy is roughly fixed through cooking, while its density per gram changes considerably.

The same principle does not hold for oil-absorbing methods: in frying, food loses water but gains oil, and total energy rises. This lesson focuses on water-based changes such as boiling, baking and grilling; frying's maths is taken up in the recipe lesson.

A change in both directions

In water-absorbing foods, energy per gram falls: raw rice carries roughly 350 kcal per 100 grams, while boiled rice sits at roughly 130 kcal per 100 grams; pasta and dried legumes dilute in a similar way. In water-losing foods, energy per gram rises: 100 grams of raw chicken breast shrinks to roughly 70-75 grams when cooked, and the same energy is packed into fewer grams. Knowing both directions matters, because the mistake can be made both ways: calculating cooked rice with the raw value inflates the estimate, and calculating meat with the raw value understates it.

The percentage differences vary from food to food; what matters here is not exact ratios but knowing the direction of the change.

Which state does this value belong to

Whenever you see a value on a label or in a food table, the first question should be: does this belong to the raw state or the cooked state? For packaged products, the 100-gram value usually describes the product as it is in the package (mostly raw or dry). Food databases, meanwhile, hold separate entries for the raw and cooked states of the same food. The most common cause of large errors in estimates is multiplying a cooked amount by a raw value, or a raw amount by a cooked value; the gap can reach two to three times.

In tracking apps this distinction usually hides in the entry's name: the difference between raw rice and boiled rice sits in the name of the line you pick, and when it goes unnoticed it shifts the whole day's total.

The consistency rule

The practical solution is a single sentence: whichever state you weighed, take the value from that same state. If you weigh dry pasta before cooking, use the raw value; if you weigh the rice on your plate, use the cooked value. Both methods are correct; what is wrong is mixing the two. In home practice, dry or raw weighing is less error-prone for most people, because cooked weight varies with how much water was absorbed, even from pot to pot.

For meat-based dishes too, the practical answer is raw weighing: since how much water cooked meat has lost varies with cooking time, a calculation based on raw weight carries fewer assumptions.