Calorie Calculator

This Calorie Calculator estimates the number of Calories you need in a day. It also provides your ideal weight range and some guidelines for weight loss or gain. This calculator is intended for adults between the ages of 18 and 80 years old. To use the calculator, please provide your age, weight, height, and activity level, then click the "Calculate" button.

What are Calories?

A Calorie (Cal) is a unit of energy, and is defined as the amount of heat needed to raise the temperature of a kilogram of water by one degree Celsius. In the context of food energy, the Calorie is the specific energy required to metabolize different types of food. This is the Calorie referenced by this calculator and the Calorie seen on nutrition labels in the United States.

Different types of foods require different amounts of energy to metabolize. The three main types of nutrients are proteins, carbohydrates, and fats. Proteins contain 4 Calories/gram, fats contain 9 Calories/gram, and carbohydrates contain 4 Calories/gram. This is the amount of energy that will be released once the body digests and absorbs the nutrients in a given food. Although it is not considered a nutrient, it is worth noting that alcohol contains 7.1 Calories/gram, and is often a significant contributing factor to weight gain/loss.

Not all Calories are created equal. It is important to consume foods that provide more nutrients per Calorie. For example, consuming 200 Calories of candy is different from consuming 200 Calories of vegetables and fruit. Vegetables and fruit contain more fiber and other nutrients while candy mostly just contains sugar. The sugar may be satisfying to consume, but the vegetables and fruit will keep you feeling satiated for longer while also providing your body with necessary nutrients. The amount of sugar the body requires in a day is extremely low, and it is easy to consume far more sugar in a day than the body actually needs. Being aware of the types of Calories we consume and regulating the consumption of less healthy Calories can have a very significant impact on weight loss/gain as well as overall health.

Calorie vs. calorie:

A Calorie and a calorie are not the same thing. The Calorie, discussed above, is also referred to as the large calorie, kilocalorie, food calorie, and kilogram calorie. To reiterate, it is the Calorie used by this calculator. The calorie on the other hand, also referred to as the small calorie or gram calorie, differs in that it is the amount of heat needed to raise the temperature of a gram (rather than kilogram) of water by 1°C. It is worth noting that the “calorie” referenced on nutrition information in the United States all reference the Calorie. The small calorie is not used within the context of food science on nutrition, so when a nutrition label says that a food contains “100 calories,” it should be read as 100 Calories in order to accurately understand the amount of energy the food will impart. In most other countries, the kilojoule is used in place of the Calorie. The kilocalorie is also used in certain countries. The kilocalorie is equivalent to the Calorie, and differ from a calorie by a factor of 1000. A Calorie equals to 4.1868 kilojoule.

How many Calories do I need a day?

The Institute of Medicine recommends that 45-65% of Calories consumed in a day should be from carbohydrates, while proteins should comprise 10-35%, and fat should comprise 20-35%. This is a very general recommendation that is meant to apply broadly to as many people as possible. As such, as an individual, the above macronutrient distribution may not necessarily be ideal. There is no one-size-fits-all recommendation, and the best course of action is to consult a nutritionist or doctor to determine individual needs.

It follows that the number of calories an individual needs to consume in a day is highly dependent on that individual. The following table provides a general guide for the number of calories a person should consume based on the Dietary Guidelines for Americans provided by the United States Department of Agriculture:

In addition to the above guidelines, Calorie calculators such as this one can be used to estimate your daily needs based on factors such as age, sex, height, weight, activity level, and desired weight goals. This will provide slightly more individualized Calorie estimates, but it is still just that, an estimate. This calculator’s estimates are based on the Mifflin-St Jeor Equation, which differs for men and women:

where W is weight in kilograms, H is height in centimeters, and A is age in years. The BMR is then multiplied by some activity factor to determine the total daily energy expenditure (TDEE), which is the number of Calories per day that you burn based on your activity level. This is the number of Calories you can consume to maintain your weight. To gain weight, you would need to consume more than this number. Similarly, to lose weight, you would have to consume less than this number. The activity factor for the various activity levels is shown in the table below:

Thus, a person with a BMR of 1350 who is active would have a TDEE of:

TDEE = 1350 × 1.55 = 2092.5

To maintain their weight, they would have to consume 2092.5 Calories per day; to lose weight they would have to consume fewer than 2092.5 Calories per day; to gain weight they would have to consume more than 2092.5 Calories per day.