Advanced BMI & Body Metric Calculator
PopularInstantCalculate your Body Mass Index (BMI) with metric or imperial units. See your exact BMI score, a color-coded health category, your prime BMI, and the healthy weight range for your height.
Your details
Your results
You are Normal
Healthy weight
56.7–76.6 kg
BMI Prime
0.91
Ponderal Index
13.1kg/m³
Healthy BMI range
18.5 – 25kg/m²
How the math works
Metric: BMI = weight(kg) / height(m)²
Imperial: BMI = 703 × weight(lb) / height(in)²Body Mass Index divides your weight by the square of your height. BMI Prime is your BMI divided by 25 (the upper end of the healthy range) — a value under 1 means you sit within the healthy band. The Ponderal Index is a related measure that uses the cube of height instead of the square, which is more reliable for very tall or very short people.
BMI classification table
| Category | BMI range (kg/m²) | Health risk |
|---|---|---|
| Severe Thinness | Below 16 | Very High |
| Moderate Thinness | 16 – 17 | High |
| Mild Thinness | 17 – 18.5 | Moderate |
| Normal | 18.5 – 25 | Low |
| Overweight | 25 – 30 | Moderate |
| Obese Class I | 30 – 35 | High |
| Obese Class II | 35 – 40 | Very High |
| Obese Class III | Above 40 | Extremely High |
What is BMI?
Body Mass Index is a simple screening measure using height and weight. Devised in the 1830s by Belgian mathematician Adolphe Quetelet, it is used worldwide as a quick indicator of whether a person is a healthy weight for their height. It applies to most adults aged 18–65.
Limitations of BMI
- Muscle vs fat: athletes can read high despite low body fat.
- Age & gender: body-fat levels differ at the same BMI.
- Ethnicity: fat distribution varies between groups.
- Children & pregnancy: BMI is interpreted differently or not applicable.
Health risks by BMI range
Underweight (< 18.5)
- Nutrient deficiencies
- Weakened immunity
- Bone loss
- Fatigue
Normal (18.5 – 25)
- Lowest chronic-disease risk
- Better heart health
- Healthy energy
- Stronger immunity
Overweight (25 – 30)
- Higher blood pressure
- Type 2 diabetes risk
- Sleep apnea
- Joint strain
Obese (> 30)
- Heart disease & stroke
- Type 2 diabetes
- Certain cancers
- Reduced life expectancy
Tips for a healthy weight
Balanced diet
Favor fruits, vegetables, whole grains, and lean protein. Limit processed foods and sugary drinks.
Regular exercise
Aim for 150 min of moderate or 75 min of vigorous activity per week, plus strength training.
Quality sleep
Target 7–9 hours a night. Poor sleep is linked to weight gain and appetite changes.
Stay hydrated
Drink water through the day — thirst is sometimes mistaken for hunger.
Mind your stress
Manage stress with movement, rest, or hobbies to curb emotional eating.
Regular checkups
Track your BMI over time with a healthcare provider for personalized guidance.
Related health metrics
BMI Prime
Your BMI divided by 25. A value of 1.0 sits at the top of the normal range; below 1.0 is normal, above is overweight.
Ponderal Index
Uses the cube of height (kg/m³) rather than the square, making it more reliable at the extremes of height.
Waist-to-Hip Ratio
Waist divided by hip circumference. Above 0.90 (men) or 0.85 (women) indicates higher abdominal-fat risk.
Body Fat Percentage
Fat mass as a share of total body mass. Essential fat is 2–5% (men) and 10–13% (women).
Frequently asked questions
What is BMI and how is it calculated?+
BMI (Body Mass Index) estimates body fat using weight and height. It is calculated as weight in kilograms divided by height in metres squared (kg/m²). For example, a person 1.75 m tall weighing 70 kg has a BMI of 70 / (1.75 × 1.75) = 22.9.
What is a healthy BMI range?+
For most adults, a BMI between 18.5 and 24.9 is considered healthy. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or above is classified as obese.
Is BMI accurate for athletes?+
BMI does not distinguish between muscle and fat, so very muscular people may register a high BMI despite low body fat. It is a useful population-level screening tool, not a diagnosis. Pair it with other measures like waist circumference or body fat percentage.
Does this calculator store my data?+
No. Every calculation runs entirely in your browser. Your height, weight, age, and gender are never sent to a server or logged.