BMI and Calorie Calculator
Enter your sex, age, weight, height and activity level to see your body mass index under both the WHO global and the WHO Asian cut-offs, together with your estimated daily calorie needs. Everything is calculated in your browser.
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How BMI is calculated
Body mass index is your weight in kilograms divided by your height in metres squared. For a person weighing 70 kg and standing 175 cm tall, the height is 1.75 m, so BMI = 70 / (1.75 x 1.75) = 22.9. The result is rounded to one decimal place.
This page shows two sets of categories side by side. The WHO global standard uses 18.5, 25 and 30 as the boundaries for underweight, overweight and obesity. The WHO 2004 Asia-Pacific standard keeps 18.5 but lowers the overweight and obese boundaries to 23 and 25, because many Asian populations carry more body fat and a higher risk of diabetes and heart disease at a lower BMI. In the example above, 22.9 is normal under both standards.
Calories: BMR and TDEE
Basal metabolic rate is the energy your body burns at rest. The calculator uses the Mifflin-St Jeor equation: 10 x weight (kg) + 6.25 x height (cm) - 5 x age + 5 for men, or minus 161 for women. For a 30 year old man with the measurements above, BMR = 700 + 1093.75 - 150 + 5 = 1648.75 kcal per day.
Total daily energy expenditure multiplies BMR by an activity factor: 1.2 for sedentary, 1.375 for light, 1.55 for moderate, 1.725 for active and 1.9 for very active. With moderate activity the same man needs about 2556 kcal per day. The tool then shows a deficit of 500 kcal for gradual weight loss and a surplus of 300 kcal for gradual weight gain. The weight loss target never drops below 1500 kcal for men or 1200 kcal for women.
Limits of BMI
BMI only compares weight with height. It cannot tell muscle from fat, so athletes can be labelled overweight, and it ignores where fat is stored. It is also less reliable for children, pregnant women, older adults and people with very high or very low muscle mass. Waist size, blood tests and a clinical assessment give a fuller picture. Calorie formulas are estimates with an error of roughly 10 percent, so adjust the numbers based on how your weight changes over several weeks.
Frequently asked questions
Which BMI standard should I use?
The WHO global standard is the most widely used. If you are of Asian descent, the Asia-Pacific cut-offs are considered more appropriate for flagging health risk earlier.
Why does my result differ between the two standards?
Both use 18.5 for underweight, but the Asian standard marks overweight from 23 and obesity from 25, so values between 23 and 30 can fall in different categories.
Is the calorie result exact?
No. It is an estimate based on a population average. Track your weight for two to three weeks and adjust your intake accordingly.
Is my data stored or sent anywhere?
No. All calculations run in your browser and nothing is uploaded.