Health & Fitness Calculator
BMI Calculator
Enter your height and weight, get your BMI, your weight category, and the healthy range for your height.
Estimated Body Fat
Deurenberg formula · enter age & gender above
BMI Value
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Category
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Healthy Weight
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BMI Prime
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BMI Classification Chart
| Category | BMI Range | Health Risk | Status |
|---|---|---|---|
| Underweight | < 18.5 | Malnutrition, osteoporosis | – |
| Normal weight | 18.5 – 24.9 | Low health risk | – |
| Overweight | 25.0 – 29.9 | Moderate health risk | – |
| Obese Class I | 30.0 – 34.9 | High health risk | – |
| Obese Class II | 35.0 – 39.9 | Very high health risk | – |
| Obese Class III | ≥ 40.0 | Extremely high risk | – |
BMI is a screening tool, not a diagnostic measure. Consult a healthcare professional for a full health assessment.
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Why FileReadyNow
Everything You Need to Track Your BMI
Metric or imperial, results as you type, no sign-up, no ads. Just your numbers.
Metric & Imperial Support
Switch between centimetres/kilograms and feet/inches/pounds with a single click. No manual conversion needed.
Updates as You Type
Your BMI, category, healthy weight range, and BMI prime update live as you change any field. No button needed.
Visual BMI Gauge
A colour-coded bar shows exactly where your BMI sits across all six WHO categories, with a pointer that moves as your numbers change.
Healthy Weight Range
See the exact weight range that counts as healthy for your height, shown in the same units you entered.
WHO Classification
Results follow the World Health Organization's six-tier BMI classification including three obesity grades.
100% Private
All calculations run in your browser. Nothing is sent to any server — your health data stays on your device.
What Is BMI?
BMI (Body Mass Index) is a number you get by dividing your weight by your height squared. It tells you whether your weight is roughly in the healthy range for your height. The formula dates back to the 1830s and was developed by Belgian statistician Adolphe Quetelet. Despite its age, it is still the most widely used weight-screening tool in medicine.
How BMI Is Calculated
The formula depends on the unit system you use:
- Metric: BMI = weight (kg) ÷ height² (m²)
- Imperial: BMI = (weight (lbs) × 703) ÷ height² (in²)
For example, someone who is 170 cm tall and weighs 70 kg has a BMI of 70 ÷ (1.70)² = 24.2, which falls in the Normal range.
WHO BMI Categories
- Under 18.5 — Underweight
- 18.5 – 24.9 — Normal weight
- 25.0 – 29.9 — Overweight
- 30.0 – 34.9 — Obese Class I
- 35.0 – 39.9 — Obese Class II
- 40.0 and above — Obese Class III (Severe)
What Is BMI Prime?
BMI Prime is just your BMI divided by 25, the upper edge of the normal range. A result of 1.0 means you are right at that boundary. Under 1.0 is normal or underweight; over 1.0 is overweight or obese. It is a quick way to see how far your BMI sits from the healthy ceiling without doing the subtraction yourself.
Limitations of BMI
BMI does not account for muscle mass, bone density, or where your body stores fat. A muscular athlete can have a BMI in the overweight range. An older adult can have a normal BMI but still carry too much body fat. Use BMI as a starting point, not a verdict, and talk to a doctor if you have concerns about your weight or health.
Step by Step
How to Use the BMI Calculator
Choose your unit system — Metric (cm/kg) or Imperial (ft, in/lbs).
Enter your height and weight. Age and gender are optional.
Results update live as you type. Hit Calculate BMI to scroll straight to the result panel.
Read your BMI value, the colour-coded gauge, and the classification table to see where you stand.
Frequently Asked Questions
BMI stands for Body Mass Index. It is a value calculated using height and weight to estimate body weight categories.
BMI is calculated by dividing weight by height squared. The exact formula depends on whether you use metric or imperial units.
BMI provides a general estimate of body weight categories. While useful, it should not replace professional medical advice or full health assessments.
Yes, the tool supports multiple measurement formats including feet, inches, pounds, centimeters, and kilograms.
Anyone interested in health, fitness, nutrition, or weight tracking can use a BMI calculator for quick insights.
Yes, the BMI Calculate feature is optimized for both desktop and mobile users for convenient access anywhere.