How to Calculate Kilocalories

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.

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.

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.

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:

• ‌Wheat bread:‌ 80 calories per slice
• ‌Tuna packed in water:‌ 109 calories per 3 oz.
• ‌Mayonnaise:‌ 94 calories per tbsp.
• ‌Pickle relish:‌ 20 calories per tbsp.

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.