How to Calculate Kilocalories

Calculate the kilocalories in a tuna sandwich by adding up the caloric amount of each ingredient.
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Kilocalories are a unit used to measure energy, and are the same thing as calories. If you're wondering how to calculate kilocalories, here are some tips to help.

What Is a Kilocalorie?

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A kilocalorie is the scientific term used to measure energy — it's the amount of heat required to increase the temperature of one kilogram of water (about a quart) by one degree Celsius, per the USDA. Kilocalories are used describe the amount of energy you eat in food or the energy you burn during exercise.

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There are two types of calories: "small" calories (cal) and "large" calories (Cal), per an August 2021 StatPearls article. A kilocalorie (kcal) is the same as one large calorie, which is equal to 1,000 small calories.

But small calories are uncommon in everyday use — large calories, or kilocalories, are what you're used to seeing on food labels and in nutrition and exercise recommendations. As a result, the two terms are used interchangeably, and there's no need to convert kcals to cals.

How Many Calories Should You Eat in a Day?

The 2020-2025 Dietary Guidelines for Americans recommends adults eat the following amounts of calories per day:

• People assigned female at birth: ‌1,600 to 2,000
• People assigned male at birth: ‌2,000 to 2,400

How to Calculate Kilocalories

You can calculate the total kilocalories in your meal or snack by adding up the calories in each ingredient.

Wondering how to find the amount of kilocalories in a particular food? Start by checking the nutrition label. If there's no label or you're eating a different amount than the recommended serving size listed on the label, use a calorie counter for the best estimate instead.

Here's an example: Say you want to make a tuna sandwich with two slices of wheat bread, one 6-ounce can of tuna packed in water, one tablespoon of mayonnaise and one tablespoon of sweet pickle relish. Per the USDA, here are the calories in each ingredient:

Next, convert the calories from the standard serving size to the amount you're eating (if necessary). For instance, two slices of wheat bread is 160 calories, and two 3-ounce servings of tuna is 218 calories.

Then add up the numbers to calculate the total calories. For the tuna sandwich, that's 160 + 218 + 94 + 20, which equals 492 calories or kilocalories.

Tip

Having a hard time converting standard serving sizes to the portion you're eating? Use the USDA's FoodData Central database for quick and easy conversions to common amounts like tablespoons, cups, cans and sticks (like butter).