1,000
kcal
320
kcal
585
kcal
0
kcal
0
kcal
1,905
kcal
7,970.5
kJ
395
g
482.3
kcal/100g
30.7
%
52.5
%
16.8
%
1,000
kcal
320
kcal
585
kcal
0
kcal
0
kcal
1,905
kcal
7,970.5
kJ
395
g
482.3
kcal/100g
30.7
%
52.5
%
16.8
%
The Caloric Value Calculator computes the total energy content of food or metabolic substrates using the Atwater system of caloric equivalents. Each macronutrient contributes a characteristic amount of energy: carbohydrates and proteins provide 4 kilocalories per gram, while fats provide 9 kilocalories per gram.
This calculation is fundamental in nutrition science, dietetics, and metabolic biology. It provides the basis for understanding energy balance, designing dietary interventions, and calculating the energy budget of organisms. The tool gives both kilocalories and kilojoules for international compatibility.
The Atwater factors for metabolizable energy are:
Carbohydrates: 4 kcal/g
Fat: 9 kcal/g
Protein: 4 kcal/g
Total caloric value is the sum of energy from each macronutrient:
Total kcal = (carbs × 4) + (fat × 9) + (protein × 4)
Conversion to kilojoules uses: 1 kcal = 4.184 kJ
Inputs
Results
A diet with 250g carbs, 65g fat, and 80g protein provides about 1,905 kcal. Carbohydrates contribute 52%, fat 31%, and protein 17% of total energy.
Inputs
Results
An athletic diet with high carbs and protein provides 2,720 kcal. The elevated protein intake supports muscle recovery and growth.
Fat molecules are more chemically reduced (higher hydrogen-to-carbon ratio) than carbohydrates, containing more energy-rich C-H bonds. When these bonds are oxidized during metabolism, more energy is released. Additionally, fats are stored in anhydrous form, while glycogen (carbohydrate storage) binds about 3g of water per gram, making fat a more energy-dense storage form.
The Atwater factors are rounded averages. Actual caloric values vary by food: different carbohydrates range from 3.7 to 4.2 kcal/g, fats from 8.4 to 9.4 kcal/g, and proteins from 3.4 to 4.4 kcal/g. Fiber provides about 2 kcal/g. For most practical purposes, the standard 4-9-4 values provide sufficiently accurate estimates.
Yes, alcohol (ethanol) provides approximately 7 kcal/g, making it the second most energy-dense macronutrient after fat. This calculator does not include alcohol, but for complete dietary analysis, alcohol calories should be added separately as: alcohol(g) × 7.
Roboculator Team
The Roboculator Team explains calculations, planning tools, and practical formulas in clear language for real-life situations.
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