Counting calories by eye is surprisingly unreliable. A "handful" of nuts can be 30 grams or 80 grams, and the difference between those two handfuls is roughly 450 calories — enough to quietly wipe out an entire day's deficit. This food calorie calculator turns a weighed portion into an exact number: pick a food, enter the grams on your plate, and the tool returns total kilocalories along with the protein, carbohydrate and fat macros for that exact weight.
Every value is scaled from the USDA FoodData Central per-100-gram reference. Because cooked foods lose water and shrink, numbers for chicken breast, rice and salmon reflect the cooked weight you actually weigh on a scale, not the raw weight you started with. Slide the portion up or down and the result updates instantly, so you can test a 50-gram snack versus a 150-gram main course before you log it.
How to Use
- Choose your Food from the dropdown. The list covers six common staples: cooked chicken breast, cooked white rice, cooked Atlantic salmon, a whole hard-boiled egg, raw broccoli, and a raw banana.
- Weigh the portion on a kitchen scale and type the grams into Portion Weight. A digital scale accurate to 1 gram is the single biggest upgrade you can make to food logging.
- Read the result card: Total Calories (kcal) is the headline number, followed by Protein, Carbohydrates and Fat in grams.
- Use Calories from Protein (protein grams × 4) to see how much of the meal's energy came from protein. Fat carries 9 kcal per gram, while protein and carbs carry 4 kcal per gram — the Atwater factors used on every US Nutrition Facts label.
- Compare two portions by re-weighing. A 70-gram chicken breast is not "a little more" than 100 grams; it is exactly 115.5 kcal with 21.7 grams of protein, which matters when you are chasing a daily protein target.
How Food Calories Are Calculated
The math is deliberately simple. Each food in the table has a known nutrient density per 100 grams, published by the USDA. To scale it to your portion:
Total nutrient = nutrient per 100 g × portion grams ÷ 100
For cooked chicken breast, the USDA lists 165 kcal, 31.0 g protein, 0 g carbs and 3.6 g fat per 100 grams. A 70-gram serving therefore delivers 165 × 70 ÷ 100 = 115.5 kcal, with 31.0 × 70 ÷ 100 = 21.7 g of protein and 3.6 × 70 ÷ 100 = 2.52 g of fat. The same formula works for every food in the dropdown.
Calories from each macronutrient follow the Atwater general factors printed on Nutrition Facts labels: protein and carbohydrate each supply 4 kcal per gram, and fat supplies 9 kcal per gram. For the 70-gram chicken, protein contributes 21.7 × 4 = 86.8 kcal, fat contributes 2.52 × 9 = 22.68 kcal, and the rest rounding accounts for the remainder of the 115.5 kcal total. Fiber, alcohol and organic acids carry their own small corrections, but for everyday logging the 4/4/9 rule is what the FDA itself uses.
Common Foods: Calories per 100 g
| Food (USDA reference) | kcal | Protein | Carbs | Fat |
|---|---|---|---|---|
| Chicken breast, cooked, roasted | 165 | 31.0 g | 0.0 g | 3.6 g |
| White rice, cooked | 130 | 2.7 g | 28.0 g | 0.3 g |
| Atlantic salmon, cooked | 208 | 20.0 g | 0.0 g | 13.0 g |
| Whole egg, hard-boiled | 155 | 13.0 g | 1.1 g | 11.0 g |
| Broccoli, raw | 34 | 2.8 g | 7.0 g | 0.4 g |
| Banana, raw | 89 | 1.1 g | 23.0 g | 0.3 g |
Notice the spread: 100 grams of broccoli is 34 kcal, while 100 grams of salmon is 208 kcal — six times the energy for the same weight. That density gap is why two bowls of the same physical size can mean completely different things for a calorie target. Weighing, not eyeballing, is what makes the number trustworthy.
Examples
Example 1 — A weighed chicken breast. You cook a skinless, boneless breast and weigh out 70 g on a scale. The calculator returns 115.5 kcal, 21.7 g protein, 0 g carbs and 2.52 g fat. Protein supplies 86.8 kcal, or about 75% of the meal's calories — a high-protein, low-fat ratio typical of lean meats.
Example 2 — A plate of rice and salmon. You weigh 200 g of cooked white rice (260 kcal, 56 g carbs) alongside 150 g of cooked salmon (312 kcal, 30 g protein, 19.5 g fat). The meal totals 572 kcal, with 56 g carbs, 30 g protein and 19.5 g fat. Fat alone contributes 175.5 kcal, or roughly 31% of the meal's calories — close to the 20–35% range the FDA Dietary Guidelines suggest for a balanced day.
Example 3 — A snack-sized banana. A medium peeled banana weighs about 118 g. Entering 118 g returns 105.02 kcal, 27.14 g carbs and 1.3 g protein. That is about 5% of a 2,000-kcal daily budget — far less than the 150–200 kcal many people estimate for a banana.
Example 4 — A large batch. Entering 1,000,000 g (one metric ton) of chicken breast returns 1,650,000 kcal and 310,000 g of protein. The engine scales linearly and never overflows on very large weights, which is the same behavior you need when you log a full meal-prep batch rather than a single plate.
FAQ
How many calories are in 100 g of chicken breast?
Cooked, skinless chicken breast contains about 165 kcal per 100 grams, with 31 grams of protein, 0 grams of carbs and 3.6 grams of fat. A 70-gram portion is therefore 115.5 kcal with 21.7 grams of protein. Values are for roasted or grilled breast without skin; breaded or fried chicken adds oil and carbs.
Why should I weigh food in grams instead of using cups?
Cups and tablespoons are volume measures, and the same food can pack very different amounts into the same cup depending on how it is chopped, packed or cooked. A cup of cooked rice is roughly 150–180 g depending on fluffiness; weighing it removes that 20% ambiguity. For calorie tracking, grams are the input that makes the number repeatable.
How do the 4/4/9 calorie factors work?
Protein and carbohydrate each provide about 4 kcal per gram, and fat provides about 9 kcal per gram. These are the Atwater general factors printed on every US Nutrition Facts panel. To split a meal into calories-from-macros, multiply protein grams by 4, carb grams by 4, and fat grams by 9. The three should sum close to the total kcal.
Is the cooked weight the same as the raw weight?
No. Most meats and grains lose water and shrink as they cook. Chicken breast loses roughly 25–30% of its raw weight during cooking, and rice roughly triples in weight as it absorbs water. This calculator uses cooked-weight USDA values, so weigh the food exactly as it sits on your plate. If you weigh raw food, look up the raw-entry value instead.
How accurate is this food calorie calculator?
The per-100-gram figures are averages from USDA FoodData Central standard reference entries. Real variation comes from the exact cut, cooking method, added oil, seasoning and ripeness. A home-cooked breast can land within about ±10% of the USDA average. Treat the result as a precise count of an average food, not a lab measurement of your exact dinner.
Can I use this to count macros for weight loss or muscle gain?
Yes — that is the intended use. Logging weighed portions gives you a repeatable record of kcal, protein, carbs and fat. Pair it with a daily calorie target (set by a TDEE calculator) and aim for a consistent surplus or deficit over weeks rather than obsessing over any single meal. The numbers here are input data, not a medical prescription.
Disclaimer
This food calorie calculator is provided for informational purposes only and is not medical advice. Values are scaled from published USDA FoodData Central averages and will vary with the specific food, cut, ripeness and cooking method. This tool does not diagnose, treat, or manage any health condition, and it is not a substitute for the advice of a registered dietitian, physician, or other qualified health professional. Always consult a healthcare professional before making significant changes to your diet, especially if you have diabetes, kidney disease, food allergies, or any other medical condition.