Calorie Calculator

How to use it

1. Choose female or male (the equations were fitted separately for each), and feet and pounds or centimeters and kilograms.
2. Enter your age, height and weight. If you know your body-fat percentage from a scan or a reliable scale, add it to refine the resting figure; the daily total does not use it.
3. Pick the activity level whose description is closest to a normal day for you. When in doubt, choose the lower one: most people overestimate how active they are.
4. Choose a goal. Maintain shows the calories that keep your weight steady; the Lose and Gain options take off or add a fixed amount a day.

Where the numbers come from

Daily needs use the equations in the 2023 Dietary Reference Intakes for Energy from the National Academies of Sciences, Engineering, and Medicine, which the United States and Canada use as their official reference. They replaced the 2005 equations and were fitted to measurements made with doubly labeled water, the most accurate way to measure what free-living people actually burn. For adults 19 and older there is a separate equation for each sex and each of four activity levels; each one takes age in years, height in centimeters and weight in kilograms. For a woman who counts as low active, for example, it is 575.77 − 7.01 × age + 6.60 × height + 12.14 × weight.

The activity levels are defined by physical activity level (total energy divided by resting energy): for adults, inactive is below 1.53, low active 1.53 to under 1.68, active 1.68 to under 1.85 and very active 1.85 to 2.5. The descriptions next to each button are Health Canada’s examples of a typical day at that level. Here is what the equations give for four example adults, before any goal is applied:

The resting figure is what your body uses lying still, from the Mifflin-St Jeor equation (1990). A 2005 systematic review for the American Dietetic Association found it predicted measured resting rate within 10% for more people, with and without obesity, than any of the other common equations. If you enter a body-fat percentage, the calculator uses the equation from the same paper based on fat-free mass instead: 19.7 × fat-free mass in kg + 413.

Losing or gaining weight

The weight-loss options are the two daily deficits the 2013 guideline from the American Heart Association, American College of Cardiology and The Obesity Society lists: 500 or 750 calories a day below what you need. The same guideline prescribes 1,200 to 1,500 calories a day for women and 1,500 to 1,800 for men on a reduced-calorie diet, and reserves diets under 800 calories for medically supervised programs. So the calculator never suggests a target under 1,200 calories for women or 1,500 for men, and it suggests no weight-loss target at all when your BMI is under 18.5.

How fast does a deficit work? The familiar rule that 3,500 calories equal a pound predicts a steady pound a week from a 500-calorie cut, for 52 pounds a year. Researchers at the National Institutes of Health showed in 2011 that this is about twice what actually happens, because the body burns less as it gets lighter. Their rule of thumb: every 10 calories a day of permanent change eventually moves weight by about a pound, about half of that change arrives in the first year, and 95% of it within about three years. That is the first-year figure the calculator shows: about 25 pounds for a 500-calorie daily cut, if it is kept up. In their worked example, a 100 kg (220 lb) sedentary man who cut 480 calories a day leveled off near 75 kg after several years.

What we tested

On October 15, 2026 we checked the page’s own functions against exact fractional arithmetic. The National Academies publish example values for US adults by age group, body size and activity level: the calculator reproduced all 128 of them for men and women at the tables’ reference ages (25, 40, 60 and 80), 124 exactly and the rest within 1 calorie, a difference explained by the tables’ rounded heights and weights. On 3,000 random adults the daily figure matched the exact calculation to the calorie, as did the resting equations and the unit conversions; on 4,004 goal cases the target, the 1,200 and 1,500 calorie limits and the BMI rule all came out as specified. In Chromium: the default woman (35, 5 ft 5 in, 150 lb, low active) showed 2,246 kcal a day and 1,376 kcal at rest, with the four activity levels 2,081 to 2,619; a 500-calorie cut showed 1,581 and about 25 lb in the first year (the 3,500-calorie rule: 52); a target under 1,200 and a weight-loss request at a BMI under 18.5 were both refused with a message; a 35-year-old man at 178 cm and 86.2 kg showed 2,968 kcal; settings survived a reload; the page fitted a 390 px phone with no errors. We also checked the check: changing one coefficient in the women’s low-active equation from 6.60 to 6.66 made the table comparison fail.

How much to trust the number

Treat the result as a starting point. Even with careful measurements, energy needs cannot be predicted for an individual much better than about 5%, and with ordinary inputs the error is larger, so two people with the same age, height and weight can differ by a few hundred calories a day. The practical test is your weight over three or four weeks: if it drifts when you expected it to hold, adjust by 100 to 200 calories and watch again. The equations are not meant for pregnancy, breastfeeding, children and teens, athletes in heavy training or people with medical conditions that change metabolism; a doctor or registered dietitian can work out needs in those cases.

Nutrient ranges

The table under the result splits the calories into the Acceptable Macronutrient Distribution Ranges for adults: 45 to 65% of calories from carbohydrate, 10 to 35% from protein and 20 to 35% from fat, at 4, 4 and 9 calories per gram. At 2,000 calories that is 225 to 325 g of carbohydrate, 50 to 175 g of protein and 44 to 78 g of fat. The recommended protein intake for adults is 0.8 g per kilogram of body weight, shown below the table.

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