What Is BMI and Why Does It Matter?

Body Mass Index (BMI) is a simple screening measure that estimates whether your weight is in a healthy range for your height. While BMI does not measure body fat directly, it's a widely used starting point for assessing general health risk. This calculator also estimates your Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE), giving you a fuller picture of your body's energy needs.

How This Calculator Works

BMI is calculated as weight (kg) divided by height in meters squared
BMR uses the Mifflin-St Jeor formula, a widely cited equation for resting energy needs
TDEE multiplies your BMR by an activity factor to estimate total daily calories burned
Waist-hip ratio (if entered) gives an additional indicator of fat distribution risk

Frequently Asked Questions

Is BMI an accurate measure of health?

BMI is a useful general screening tool, but it doesn't account for muscle mass, bone density, or fat distribution. Athletes, for example, may have a high BMI despite low body fat. Use it alongside other measures like waist-hip ratio for a fuller picture.

What is a healthy BMI range?

For most adults, a BMI between 18.5 and 24.9 is considered within the normal weight range. Below 18.5 is classified as underweight, and 25 and above is classified as overweight or obese, depending on the value.

What's the difference between BMR and TDEE?

BMR is the number of calories your body burns at complete rest just to maintain basic functions. TDEE adds your activity level on top of that to estimate your total daily calorie needs.

Is my data stored anywhere?

No. All calculations happen directly in your browser using JavaScript. Nothing you enter is sent to or stored on our servers.

BMI Calculator