BMI Calculator — Calculate Body Mass Index & Healthy Weight
Free online BMI calculator for men, women, and teens. Calculate your exact Body Mass Index, BMI Prime, Ponderal Index, and healthy weight range in metric or imperial units.
How to use this calculator
👉 Fill in the boxes below and your answer appears instantly — no maths needed, we do it all for you! 🎉
In plain English — what does this do?
🏋️ Your body needs food to move, breathe, and grow — just like a car needs petrol. This tool helps you find out how much food your body needs in a day to feel good and stay healthy!
A BMI (Body Mass Index) calculator evaluates your body mass relative to your height to determine if your weight falls within underweight, normal, overweight, or obese ranges according to WHO criteria. It also computes BMI Prime and Ponderal Index for advanced health assessment.
Your BMI Score is 📊
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BMI Prime
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Ponderal Index
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Healthy Weight Range
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| WHO Category | BMI Range |
|---|---|
| Severe Thinness | < 16.0 |
| Moderate Thinness | 16.0 – 16.9 |
| Mild Thinness | 17.0 – 18.4 |
| Normal | 18.5 – 24.9 |
| Overweight | 25.0 – 29.9 |
| Obese Class I | 30.0 – 34.9 |
| Obese Class II | 35.0 – 39.9 |
| Obese Class III | ≥ 40.0 |
What is BMI Calculator — Calculate Body Mass Index & Healthy Weight?
A BMI (Body Mass Index) calculator evaluates your body mass relative to your height to determine if your weight falls within underweight, normal, overweight, or obese ranges according to WHO criteria. It also computes BMI Prime and Ponderal Index for advanced health assessment.
How to use it
- 1️⃣ Select your preferred measurement units: Metric (cm, kg) or Imperial (feet, inches, lbs).
- 2️⃣ Enter your age, biological sex, height, and body weight.
- 3️⃣ Read your exact BMI score, WHO weight category, BMI Prime score, and Ponderal Index.
- 4️⃣ Review your personalized healthy weight target range based on your exact height.
Formula & Variables
Variable Definitions:
💡 See it in action — a real example
📊 World Health Organization (WHO) BMI Classification for Adults
International standard weight status categories established by the WHO for adults aged 20 and older.
| Category | BMI Range (kg/m²) | BMI Prime | Health Risk Profile |
|---|---|---|---|
| Severe Thinness | < 16.0 | < 0.64 | Very High risk of malnutrition & complications |
| Moderate Thinness | 16.0 – 16.9 | 0.64 – 0.67 | Moderate risk of nutritional deficiencies |
| Mild Thinness | 17.0 – 18.4 | 0.68 – 0.73 | Slight risk of osteoporosis & fatigue |
| Normal / Healthy Weight | 18.5 – 24.9 | 0.74 – 0.99 | Lowest health risk & optimal longevity |
| Overweight (Pre-obese) | 25.0 – 29.9 | 1.00 – 1.19 | Increased risk of cardiovascular issues |
| Obese Class I (Moderate) | 30.0 – 34.9 | 1.20 – 1.39 | High risk of type 2 diabetes & hypertension |
| Obese Class II (Severe) | 35.0 – 39.9 | 1.40 – 1.59 | Very High risk of metabolic complications |
| Obese Class III (Morbid) | ≥ 40.0 | ≥ 1.60 | Extremely High risk of chronic illnesses |
* Standard cutoffs apply to men and women regardless of age. Asian populations may face elevated cardiometabolic risk at lower BMI thresholds (≥ 23.0 for overweight, ≥ 27.5 for obesity).
📊 Health Risks Associated with BMI Extremes
Clinical health consequences documented for individuals outside normal weight boundaries.
| BMI State | Documented Medical Risks | Recommended Action |
|---|---|---|
| Underweight (< 18.5) | Malnutrition, anemia, osteoporosis, weakened immune function, fertility complications | Nutrient-dense caloric surplus, resistance training, doctor consultation |
| Normal (18.5 – 24.9) | Lowest all-cause mortality, balanced blood pressure, normal insulin sensitivity | Maintain balanced diet, regular physical exercise (150 min/week) |
| Overweight (25 – 29.9) | Elevated LDL cholesterol, borderline hypertension, increased joint strain | Mild 300–500 calorie deficit, daily cardio activity, whole food nutrition |
| Obese (≥ 30.0) | Type 2 diabetes, coronary artery disease, sleep apnea, osteoarthritis, fatty liver disease | Supervised medical lifestyle intervention, structured nutrition plan |
❓ Common questions
- What is a healthy BMI chart for adult men and women?
- According to the World Health Organization (WHO), a healthy adult BMI ranges from 18.5 to 24.9. A BMI under 18.5 is categorized as underweight, 25.0–29.9 as overweight, and 30.0 or above as obese.
- How do I calculate BMI manually?
- To calculate BMI in metric units, divide your weight in kilograms by your height in meters squared (kg/m²). In imperial units, divide your weight in pounds by height in inches squared, then multiply by 703.
- What is a healthy BMI for adults over 60?
- While WHO standard categories apply to all adults 20 and older, clinical studies suggest a slightly higher BMI range of 23.0 to 27.0 may be protective for adults over 65 against bone loss and illness.
- What is the difference between BMI and Body Fat Percentage?
- BMI measures total weight relative to height but cannot distinguish between muscle and body fat. Body Fat Percentage measures the exact proportion of fat tissue vs lean tissue in your body.
- What is BMI Prime?
- BMI Prime is the ratio of your actual BMI to the upper limit of normal BMI (25.0). A BMI Prime of 1.00 indicates you are exactly at the maximum normal weight threshold. A ratio above 1.00 indicates overweight.