BMI Calculator

What Is BMI?

Body Mass Index (BMI) is a simple screening measure that uses your height and weight to estimate whether you fall into an underweight, normal, overweight, or obese range. It's the same formula doctors' offices and public health bodies like the WHO and CDC use for a quick, population-level check — not a diagnosis.

How BMI Is Calculated

BMI = weight (kg) ÷ height (m)². In imperial units: BMI = 703 × weight (lb) ÷ height (in)².

• Underweight: below 18.5
• Normal weight: 18.5–24.9
• Overweight: 25–29.9
• Obese: 30 and above

Example

A person weighing 70 kg at 1.75 m tall: 70 ÷ (1.75 × 1.75) = 22.9 → Normal weight.

Tracking a weight goal? Use our Date Calculator to count down the days to your target date, or the Percentage Calculator to see what percentage of your starting weight you have lost so far.

Learn more: How to Calculate BMI: A Complete Guide, Ideal Weight vs BMI, and How Often Should You Check Your BMI?, and How BMI Calculations Differ for Athletes and Muscular Body Types

FAQ

Is BMI accurate for athletes or muscular people? Not always. BMI doesn't distinguish muscle from fat, so muscular individuals can show as "overweight" despite low body fat. It's a screening tool, not a diagnosis.

Does BMI apply the same way to children? No. Children and teens are measured against age- and sex-specific percentile charts, not the adult categories shown here.

Can BMI be too low even in the "normal" range? Yes — frame size, age, and muscle mass mean two people with the same BMI can have very different health profiles. Use BMI as a starting point, not a final answer.

How often should I check my BMI? There's no fixed rule — most people check it occasionally alongside other health markers rather than tracking it daily.