Free BMI Calculator
Find your body mass index in seconds. Enter your weight and height, choose metric or imperial units and see your BMI and weight category right away.
Quick Answer: What Is Your BMI?
Your BMI is your weight divided by your height squared. Worked example: 70 kg and 1.75 m gives 70 / (1.75 x 1.75) = 22.9, which is in the normal weight category for adults. In imperial units, 154 lb and 69 inches gives 703 x 154 / (69 x 69) = 22.7, also normal weight. This tool shows your BMI and your adult category only. It does not give a personal weight range in kilograms for your height, and it does not measure body fat. Adult ranges are underweight below 18.5, normal weight 18.5 to 24.9, overweight 25 to 29.9 and obese 30 and above. Use it as a screening number, not a diagnosis, and check your BMR calculator result beside it.
How to use the Free BMI Calculator
- Choose your units: metric (kg and cm) or imperial (lb and inches).
- Enter your weight in the first box and your height in the second.
- Press Calculate BMI to see your body mass index and weight category instantly.
BMI categories for adults
Your result falls into one of four standard categories used by health organizations worldwide:
| Category | BMI range (kg/m²) |
|---|---|
| Underweight | Below 18.5 |
| Normal weight | 18.5 - 24.9 |
| Overweight | 25 - 29.9 |
| Obese | 30 and above |
How BMI is calculated
The BMI formula is simple: divide your weight in kilograms by your height in meters squared.
BMI = weight (kg) ÷ height (m)²
For example, a person who weighs 70 kg and is 1.75 m tall has a BMI of 70 ÷ (1.75 × 1.75) ≈ 22.9 - comfortably in the normal range. If you use pounds and inches, the formula is 703 × weight (lb) ÷ height (in)². This calculator does the conversion for you automatically.
Limitations of BMI
BMI is a screening tool, not a diagnosis. It compares your total weight to your height but cannot tell muscle apart from fat, so athletes and people with a muscular build can land in the "overweight" range while being perfectly healthy. It also does not account for age, sex, bone density or where fat is stored - factors that matter for real health risk. Older adults naturally carry more fat at the same BMI, and the standard ranges do not apply to children and teens.
Treat your result as a starting point. If your BMI is outside the normal range, a doctor or dietitian can look at the full picture - waist circumference, blood work and lifestyle - before drawing any conclusions.
Frequently asked questions
BMI equals your weight in kilograms divided by your height in meters squared. With pounds and inches, the result is multiplied by 703.
For adults, 18.5 to 24.9 is generally considered the normal range.
Not always. BMI does not separate muscle from fat, so very muscular people can show a high BMI while being healthy.
No. This tool uses adult ranges. Children and teens are measured against growth charts for their age, so ask a doctor.
More free tools: BMR Calculator and Age Calculator.