The grams to calories calculator is a simple tool that allows you to convert the amount of macronutrients (expressed in grams) into calories. The article below shows how to convert grams to calories and how many calories there are in a gram of carbohydrate, protein, fat, and alcohol.

Not sure how many grams of each macronutrient you should consume daily? Check out our macro calculator!

Grams to calories conversion

Almost all food labels have information stating the number of total calories and grams of macronutrients, but you will rarely see the number of calories from each macronutrient. This grams to calories calculator helps you to understand the difference between calories and grams, and learn the conversion rules.

Knowing how to convert grams to calories allows you to:

How many calories in a gram of carbohydrate?

Carbohydrates are the main source of energy in the human diet. They include sugars, starches, and fiber.

Carbohydrates consumed in food provide 3.87 kcal of energy per gram for simple sugars, and 3.57 - 4.12 kcal per gram for complex carbohydrates. These values are usually rounded to 4 kcal per gram of carbohydrate to simplify the calculation.

How many calories in a gram of protein?

Proteins are the major functional and structural component of every animal cell. They consist of amino acids, some of which humans cannot synthesize. It means you must obtained proteins from your diet.

As with every macronutrient, they also provide energy - 1 gram of protein provides approximately 4 kcal.

How many calories in a gram of fat?

Fat is the most energy-dense macronutrient - 1 gram provides 9 kcal.

You need fats for the construction and maintenance of cell membranes, to maintain a stable body temperature, and to supply fat-soluble vitamins.

How many calories in a gram of alcohol?

Alcohol contains quite a lot of calories – 7 calories per gram. The amount of alcohol consumed in grams may not be possible to find on the label, but, don't worry, there is an easy way to calculate it using the information provided on every product! Our grams to calories calculator uses the formula below to do it for you:

alcohol [g] = volume [ml] * alcohol by volume [%] * volumetric mass density [g/mL]

The last variable is constant and equals 0.78924 g/mL for alcohol, so we can also present the equation as follows:

alcohol [g] = volume [ml] * alcohol by volume [%] * 0.78924 [g/mL]

Calorie (cal) and kilocalorie (kcal) - is that the same?

Have you ever wondered if the phrase grams to calories and grams to kcal mean the same thing? We are here to give you the answer.

There are two main definitions of a calorie:

  1. Small calorie or gram calorie (we usually denote it as cal).
  2. Large calorie, food calorie, or kilocalorie (which we present as Cal, calorie, or kcal).

In nutrition, we commonly use the word calorie to mean the number of kilocalories (kcal) when providing nutritional information, therefore our grams to calories calculator uses the phrases grams to calories and grams to kcal interchangeably.

Convert grams to calories - practical example

Let's convert grams to calories using the following nutritional information as an example.

Macronutrient
Grams
Carbohydrates
23
Protein
4
Fat
9

To calculate the number of calories in this food product, you need to use the appropriate conversion rate for each macronutrient:

Carbohydrate: 4 kcal * 23 = 92 kcal

Protein: 4 kcal * 4 = 16 kcal

Fat: 9 kcal * 9 = 81 kcal

Total: 92 kcal + 16 kcal + 81 kcal = 189 kcal

This product contains 189 kcal. But what can you use this information for?

or

  • If you calculate the calories in each macronutrient consumed, you will find out if you should maintain, lose, or gain weight.
Joanna Michałowska, PhD candidate