Calculate Body Mass Index with gender, age, and metric or US/UK units. See BMI category, health risk level, healthy weight range, adult and child CDC reference tables, and an interactive chart.
Read: BMI Calculator Guide: Formula, Categories & Healthy Range →
Select US/UK (feet, inches, pounds) or metric (cm, kg). Enter age for child percentile guidance.
Provide height and weight. Click Calculate to see BMI, category, and healthy weight range.
Adults use fixed BMI ranges; ages 2–19 use CDC percentiles. BMI screens weight status — it does not diagnose body fat.
Body Mass Index (BMI) relates your weight to your height. It is expressed in kg/m² regardless of which units you enter.
The BMI in kg/m² is equal to the mass in kilograms (kg) divided by the square of height in meters (m):
Example: 70 kg and 1.75 m → BMI = 70 ÷ 1.75² = 22.9
The BMI in kg/m² is equal to the mass in pounds (lb) divided by the square of height in inches (in), times 703:
Example: 154 lb and 67 in (5′7″) → BMI = (154 ÷ 67²) × 703 = 24.1
| BMI Category | BMI Range (kg/m²) | Health risk |
|---|---|---|
| Underweight | 18.4 and below | Malnutrition risk |
| Normal weight | 18.5 – 24.9 | Low risk |
| Overweight | 25 – 29.9 | Enhanced risk |
| Moderately obese | 30 – 34.9 | Medium risk |
| Severely obese | 35 – 39.9 | High risk |
| Very severely obese | 40 and above | Very high risk |
For children and teens, BMI is interpreted using age- and sex-specific percentiles (CDC growth charts), not fixed adult cutoffs.
| BMI Category | BMI Percentile | Health risk |
|---|---|---|
| Underweight | Less than 5th percentile | Malnutrition risk |
| Normal weight | 5th percentile to less than 85th percentile | Low risk |
| Overweight | 85th percentile to less than 95th percentile | Enhanced risk |
| Obese | 95th percentile and greater | High risk |
Reference chart for adults — colored zones show underweight, normal, overweight, and obese ranges by height and weight.
Enter height and weight, then click Calculate.
Switch between metric and imperial measurements.
Underweight, normal, overweight, and obese ranges.
See the weight range for a normal BMI at your height.
Health data never leaves your browser.
WHO classifies 18.5–24.9 kg/m² as normal weight for adults age 20 and older. Below 18.5 is underweight; 25+ is overweight.
For ages 2–19, BMI is compared to CDC growth chart percentiles by age and sex — not fixed adult cutoffs.
Muscular individuals may have higher BMI without excess fat. Use BMI as one screening tool alongside professional advice.
The calculator shows the weight range that corresponds to BMI 18.5–24.9 at your height.
Yes. Free with unlimited calculations and no signup; health data stays on your device.
Health questionnaires, fitness tracking, and pediatric checkups reference BMI — but adult and child interpretations differ. This calculator handles both with CDC categories, healthy weight ranges, and unit flexibility.
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