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About this tool
Basal metabolic rate (calories at rest) via the Mifflin-St Jeor equation, plus daily needs.
This BMR Calculator estimates the calories your body burns at complete rest using the Mifflin-St Jeor equation — 10 x weight in kg plus 6.25 x height in cm minus 5 x age, then +5 for men or -161 for women — and multiplies it by an activity factor from 1.2 to 1.9 to give your total daily energy expenditure. From that it builds a target for losing or gaining 0.25 to 0.5 kg a week, splits the calories 25 percent protein, 45 percent carbohydrate and 30 percent fat, and adds BMI, a Deurenberg body-fat estimate and protein and water targets. It is a planning estimate for healthy adults, not a clinical measurement.
Open BMR Calculator on AltFTool — it loads instantly in your browser.
Select your sex to begin the calculation, as this influences the basal metabolic rate due to differences in body composition and metabolism.
Enter your weight in kilograms and height in centimeters to provide the calculator with the necessary metrics to estimate your body's energy expenditure.
Input your age, as metabolic rate decreases with age, to finalize the calculation and receive your personalized daily calorie needs.
Runs Mifflin-St Jeor rather than the older Harris-Benedict formula, which generally overestimates resting expenditure in today's populations.
Converts your chosen calorie goal into protein, carb and fat grams at 4, 4 and 9 kcal per gram, then splits the day 25/35/30/10 across breakfast, lunch, dinner and snacks.
Weight-loss targets are clamped at 1,200 kcal a day, so a large deficit on a small frame does not silently produce an unsafe number.
BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age in years) + 5 for men, or - 161 for women. For a 30-year-old man of 175 cm and 68 kg that gives about 1,629 kcal a day. It is the equation most dietitians now use in place of Harris-Benedict.
Sedentary is 1.2 for little or no exercise, lightly active 1.375 for 1-3 days a week, moderate 1.55 for 3-5 days, very active 1.725 for 6-7 days, and extra active 1.9 for hard training plus a physical job. Most people overestimate here, so if you are between two levels the lower one usually tracks reality better.
The tool subtracts 500 kcal a day from your TDEE for roughly 0.5 kg a week and 250 kcal for roughly 0.25 kg, based on the convention that about 7,700 kcal equals a kilogram of body mass. Losses of 0.25 to 0.5 kg per week are the range generally considered sustainable; faster drops tend to cost lean tissue.
It is a rough estimate from the Deurenberg equation, which derives body fat from BMI, age and sex: 1.20 x BMI + 0.23 x age - 16.2 for men or - 5.4 for women. Because it starts from BMI it inherits BMI's blind spot and will read high for muscular people and low for those with little muscle — DEXA or a skinfold measurement is far more reliable.
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