No scale? Start from a photo. Free to download; photo logging needs premium.
Guide Facts
General information, not medical advice. By the Calco Editorial Team.
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Medical disclaimer: this is general information, not medical advice. Follow your doctor, prescriber, or registered dietitian. Read our editorial policy.
To count calories in food without a label, find the weight of each food, look up its calories per 100 g in USDA FoodData Central, and multiply. For a homemade dish, divide the total calories by the cooked weight. With no scale, estimate portions by eye or from a photo, then adjust. Each method below has a worked example with USDA values.
The 4 methods at a glance
| Method | What you need | Best for |
|---|---|---|
| 1. Weigh and look up | A kitchen scale and USDA FoodData Central | Single foods at home |
| 2. Recipe math | The weight of each ingredient and of the cooked dish | Soups, stews, casseroles, batch cooking |
| 3. Portions by eye | Common objects as a size guide | Eating out, eating at a friend's home |
| 4. Photo estimate, then adjust | A photo-logging app | Mixed plates when you have no time to weigh |
Method 1 is the most precise, because it uses a measured weight. Methods 3 and 4 are estimates. Use them when you cannot weigh, and correct them when you know more.
Method 1: weigh the food and look it up in USDA FoodData Central
- Weigh each food on its own, in grams.
- Search USDA FoodData Central for the food in the same state you weighed it (cooked or raw).
- Multiply: calories = calories per 100 g × grams ÷ 100.
Worked example: a home-cooked chicken and rice plate
| Food | Weight | kcal per 100 g | kcal | Protein | USDA source |
|---|---|---|---|---|---|
| Chicken breast, roasted | 150 g | 165 | 248 | 46.5 g | FDC 171477 |
| White rice, cooked | 180 g | 130 | 234 | 4.8 g | FDC 168878 |
| Olive oil | 10 g | 884 | 88 | 0 g | FDC 171413 |
| Romaine lettuce | 60 g | 17 | 10 | 0.7 g | FDC 169247 |
Total: about 580 kcal, 52 g protein, 16 g fat and 53 g carbohydrate. Note the oil: 10 g of olive oil adds 88 kcal, more than a third of the rice.
Method 2: count calories in a homemade recipe
For a dish you cook in one pot, count the whole pot, then take your share by weight.
- Weigh each ingredient and add up the calories (method 1).
- Weigh the finished dish. Weigh the empty pot first, then subtract it.
- Divide: calories per gram = total calories ÷ cooked weight.
- Weigh your portion and multiply.
Worked example: a pasta and beef bake
| Food | Weight | kcal per 100 g | kcal | Protein | USDA source |
|---|---|---|---|---|---|
| Pasta, cooked | 500 g | 158 | 790 | 29 g | FDC 169737 |
| Ground beef 85% lean, cooked | 400 g | 256 | 1024 | 110.8 g | FDC 174034 |
| Cheddar cheese | 60 g | 410 | 246 | 14.5 g | FDC 170899 |
| Olive oil | 15 g | 884 | 133 | 0 g | FDC 171413 |
- Total: about 2193 kcal for the whole dish.
- Cooked weight of the dish: 975 g (in this example, the sum of the cooked ingredients).
- Calories per gram: 2193 ÷ 975 = 2.25 kcal/g.
- Your portion: 325 g × 2.25 = about 731 kcal, with about 51 g protein.
This method also works when someone else cooks for you, if they can tell you the ingredients. For our step-by-step method at restaurants, see how to track calories when eating out.
Method 3: estimate portions by eye
No scale? Compare the portion with a common object. The NHLBI serving size card (archived copy) gives these sizes; MedlinePlus gives similar comparisons (a deck of cards for one serving of meat, a baseball for 1 cup of chopped vegetables):
- 3 ounces (about 85 g) of meat, fish or poultry is about the size of a deck of cards.
- 1 cup of salad greens is about the size of a baseball.
Worked example: a chicken breast the size of two decks of cards is about 170 g. At 165 kcal per 100 g (USDA), that is about 281 kcal.
An estimate by eye can be wrong in either direction. Weigh the same food at home now and then to check your eye.
Method 4: estimate from a photo, then adjust
A photo-logging app estimates the foods and portions on your plate from a picture. In Calco (our app), you snap a photo of the meal, and the AI estimates calories and macros (protein, carbs, fat). You can then adjust each portion.
Use the photo estimate as a first draft:
- Take the photo before you eat, with the whole plate in view.
- Check each food in the estimate. Change a portion that looks wrong.
- Add what the photo cannot see, such as oil, butter or sugar cooked into the food.
The result is an estimate, not a measurement. Photo logging in Calco requires the premium subscription; Calco is free to download and runs on iPhone only.
Two mistakes that change the count the most
1. Cooked weight with raw values (or the opposite). Rice gains water when it cooks. USDA lists cooked white rice at 130 kcal per 100 g (USDA) and raw white rice at 365 kcal per 100 g (USDA). 180 g of cooked rice is about 234 kcal. If you use the raw value for the same 180 g, you log about 657 kcal. Always match the USDA entry to the state you weighed.
2. Forgetting the cooking fat. Fat has the most calories per gram. USDA lists olive oil at 884 kcal per 100 g (USDA) and salted butter at 717 kcal per 100 g (USDA). So 10 g of oil is about 88 kcal, and 10 g of butter is about 72 kcal. Weigh the oil bottle before and after you cook to find how much went in.
Conclusion
Weigh and look up when you can, use recipe math for one-pot dishes, and estimate by eye or by photo when you cannot weigh. Match the USDA entry to cooked or raw, and always count the cooking fat.
Frequently asked questions
How do you count calories in food without labels?
Weigh the food, find its calories per 100 g in USDA FoodData Central, and multiply by the grams divided by 100. Without a scale, estimate the portion by eye or from a photo, then adjust.
How do I count calories in homemade food?
Add up the calories of all ingredients, weigh the finished dish, and divide to get calories per gram. Then weigh your portion and multiply. The pasta bake example on this page shows the math.
How can I estimate calories in food without a scale?
Compare the portion with a common object: 3 ounces of meat is about a deck of cards, and 1 cup of salad greens is about a baseball (NHLBI). Then look up the food in USDA FoodData Central.
Should I weigh food cooked or raw?
Either works if the USDA entry matches. Cooked rice and raw rice have very different values per 100 g (cooked, raw). Pick the entry for the state you weighed.
Can an app count calories from a photo?
Some apps estimate calories from a photo. In Calco, the AI estimates calories and macros, and you can adjust the portion. It is an estimate, not a measurement. Photo logging in Calco requires the premium subscription.
Related guides
Topics: Calorie Counting, USDA FoodData Central, Homemade Food, Portion Size, Food Scale.
