One of the quietest errors in a food log is weighing food cooked and logging it as raw, or the other way around. Both entries are correct. They describe different weights of the same food, because cooking changes how much water is in it.
The short version
- Cooking changes a food's weight, mostly by water going out or in. The calories in the whole portion stay about the same.
- Log in the state you weighed: raw weight with a raw entry, cooked weight with a cooked entry.
- If you can, weigh raw before cooking. It is steadier than guessing a cooked weight.
Real numbers per 100 grams
These come from USDA FoodData Central, SR Legacy data, which is also the dataset behind Vital's common-food search.
| Food | Raw or dry | Cooked |
|---|---|---|
| Chicken breast, skinless, boneless, meat only | 120 kcal, 22.5 g protein (73.9% water) | Grilled: 151 kcal, 30.5 g protein (66.1% water) |
| White rice, long-grain, regular | 365 kcal, 7.13 g protein (11.6% water) | 130 kcal, 2.69 g protein (68.4% water) |
| Pasta, enriched | 371 kcal, 13.0 g protein (9.9% water) | 158 kcal, 5.8 g protein (62.1% water) |
Rice and pasta soak up water, so a gram of cooked rice holds about 2.8 times fewer calories than a gram of dry rice, and pasta about 2.3 times fewer. Chicken loses water, so a gram of cooked chicken holds about a quarter more calories than a gram of raw.
What a mix-up costs
- You weigh 150 g of cooked rice and log it with the raw entry: 150 x 3.65 = 548 calories. The right number is 150 x 1.30 = 195. You have counted 353 calories that were never on the plate.
- You weigh 150 g of grilled chicken and log it with the raw entry: 150 x 1.20 = 180 calories and 34 g of protein. The right numbers are 227 calories and 46 g. You have missed about a fifth of the calories and a quarter of the protein.
What a cooking yield is
The USDA defines a cooking yield as 100 x (cooked weight / raw weight), and publishes tables of yields along with how much moisture and fat changed. If you know the yield, you can convert. If you do not, estimate your own: weigh a batch raw, cook it, weigh it again.
You can also work a yield out from the water figures above, if you assume only water changes. Rice: 100 g raw holds 88.4 g of dry matter, and cooked rice is 31.6% dry matter, so 100 g raw becomes about 280 g cooked. That matches the 2.8 times in calories. For grilled chicken the same arithmetic gives about 77 g cooked from 100 g raw. Fat that drips away would lower the real yield, so treat it as an estimate.
A simple rule
- Pick the database entry that matches the state you weigh in, raw or cooked.
- For batch cooking, weigh the batch raw, then weigh the pot after cooking. A portion's raw weight is its cooked weight divided by the cooked weight of the batch, times the raw weight of the batch. If 600 g of raw rice cooks to 1,680 g and you eat 300 g, that is 300 / 1,680 x 600 = 107 g raw, about 391 calories. The cooked entry gives the same answer: 300 x 1.30 = 390.
- Log oil, butter and sauces separately. The entries above are for the plain food.
In Vital, common foods come from USDA SR Legacy, which lists raw and cooked versions as separate foods. Pick the one that matches how you weighed.
What we are less sure about
- Averages, not your chicken. USDA values come from samples. Cut, time, temperature and doneness all change the yield, and the USDA's own tables report different yields for different cuts and methods.
- Fat is a moving part. For ground beef, the USDA tracks the change in fat as well as water, because it depends on how much is drained. A cooked ground beef entry assumes a particular way of cooking.
- Mixed dishes. Once oil, sauce, bones or skin are involved, a single conversion will not be exact. A recipe entry is a better fit than adding up cooked parts.
- Rice and pasta vary. How much water they absorb depends on the type and the cooking time, so the 2.8 is typical rather than fixed.
Sources
- U.S. Department of Agriculture. FoodData Central, SR Legacy: chicken, broiler or fryers, breast, skinless, boneless, meat only, raw (FDC ID 171077) and cooked, grilled (FDC ID 171534). Public domain. raw entry
- U.S. Department of Agriculture. FoodData Central, SR Legacy: rice, white, long-grain, regular, raw, enriched (FDC ID 168877) and cooked (FDC ID 168878). Public domain. raw entry
- U.S. Department of Agriculture. FoodData Central, SR Legacy: pasta, dry, enriched (FDC ID 169736) and pasta, cooked, enriched, without added salt (FDC ID 169737). Public domain. dry entry
- U.S. Department of Agriculture, Agricultural Research Service. USDA Table of Cooking Yields for Meat and Poultry, Release 2. Nutrient Data Laboratory, September 2014. PDF
Written November 5, 2026. This is general information, not medical advice. Talk to a doctor or dietitian before big changes to how you eat or train, especially with a medical condition or a history of disordered eating.