BMI Calculator
Calculate your Body Mass Index instantly using metric or imperial units. Free, accurate, and private.
BMI Categories
| BMI Range | Category | Health Risk |
|---|---|---|
| Below 18.5 | Underweight | Increased risk |
| 18.5 – 24.9 | Normal weight | Minimal risk |
| 25.0 – 29.9 | Overweight | Increased risk |
| 30.0 and above | Obese | High risk |
How to Use
- Select your preferred unit system — metric (kg/cm) or imperial (lbs/ft).
- Enter your weight and height in the fields provided.
- Click "Calculate BMI" to see your result, category, and healthy weight range.
Frequently Asked Questions
What is BMI?
BMI (Body Mass Index) is a measure of body fat based on height and weight. It's calculated by dividing weight in kg by height in metres squared (kg/m²). It's widely used as a screening tool for weight categories.
Is BMI accurate for everyone?
BMI is a useful screening tool but has limitations. It doesn't directly measure body fat and can be misleading for athletes, elderly individuals, or people with high muscle mass. Always consult a healthcare provider for a full health assessment.
What is a healthy BMI?
A BMI between 18.5 and 24.9 is considered healthy for most adults. However, optimal BMI can vary by age, sex, and ethnicity.
Is my data private?
Yes. All calculations happen entirely in your browser. No data is sent to any server.
What Is BMI and How Is It Calculated?
BMI — Body Mass Index — is a numerical value calculated from your height and weight. It was developed in the 1830s as a simple population-level screening tool. Today it is used by doctors and health organisations worldwide as an initial indicator of whether a person's weight may be putting their health at risk.
| Unit System | Formula | Example |
|---|---|---|
| Metric | BMI = weight (kg) ÷ height² (m) | 70kg ÷ (1.75 × 1.75) = 22.9 |
| Imperial | BMI = (weight (lbs) ÷ height² (in)) × 703 | (154 ÷ 4761) × 703 = 22.7 |
BMI Limitations — What It Doesn't Tell You
BMI is a useful starting point but it has well-documented limitations. Understanding these helps you interpret your result correctly.
| Group | Why BMI May Be Misleading | Better Measure |
|---|---|---|
| Athletes | High muscle mass pushes BMI into "overweight" despite being very fit | Body fat percentage |
| Elderly people | Muscle loss with age means BMI can read "normal" while body fat is actually high | Waist circumference + fat % |
| Pregnant women | Weight gain during pregnancy is normal — BMI is not a useful indicator | Gestational weight charts |
| Children | Standard adult BMI categories do not apply to children — growth stage must be considered | BMI-for-age percentile charts |
Frequently Asked Questions
What is BMI and how is it calculated?
What is a healthy BMI for adults?
Is BMI accurate for everyone?
What BMI range is considered obese?
Can I use this calculator for children?
Is my data private?
How often should I check my BMI?
Health Disclaimer: The BMI calculator on ToolsNest is provided for informational purposes only. BMI is a screening tool, not a medical diagnosis. Results should not be used as a substitute for professional medical advice. Always consult a qualified healthcare provider regarding any health concerns.