Free & Instant BMI Calculator (Body Mass Index)
Use our free BMI calculator to find your Body Mass Index quickly and see whether you’re underweight, healthy, overweight, or obese. Available in metric and imperial units
⚠️ Advisory only: BMI is a population measure and doesn’t diagnose health. For medical advice, consult a professional.
Calculate Your BMI in Kilograms and Centimetres
Your BMI will appear here
Enter your height and weight, then select Calculate.
What your result means
Enter valid values to see guidance.
Handling Metric (kg/cm) and Imperial (lb/ft) Units
Our BMI calculator is designed for global use, allowing you to seamlessly calculate your Body Mass Index using either the Metric System (kilograms and centimeters) or the Imperial System (pounds and feet/inches). Simply select your preferred unit type above. The tool automatically performs the necessary conversions to ensure your result is accurate and presented in the standard kg/m² format, making the calculation process fast and error-free.
Why Use This BMI Calculator?
Instant & lightweight
No sign‑ups. Results update as you type.
Metric & imperial
Toggle kg/cm ↔ lb/ft/in with automatic conversion.
Healthy range
Shows the healthy weight range for your height.
Shareable
Copy a link that preserves your inputs and result.
How to Calculate Your BMI in 3 Steps?
Select units
Metric (kg, cm) or Imperial (lb, ft/in).
Enter height & weight
Adjust decimals if you like.
Read your BMI & range
Then explore the worked example.
How to Use This BMI Calculator
How BMI works
BMI compares your weight to your height using a simple ratio. It’s a widely used population measure to screen for underweight, healthy weight, overweight and obesity. It doesn’t directly measure body fat or health, so factors like muscle mass, age, sex and ethnicity can influence interpretation.
How Your BMI is Calculated (Metric and Imperial Formulas)
- Metric:
BMI = kg / m² - Imperial:
BMI = 703 × lb / in² - Healthy range (adults):
18.5 – 24.9(Under 18.5 = underweight, 25–29.9 = overweight, ≥30 = obesity)
Worked example (metric): Height = 170 cm (1.70 m), Weight = 65 kg → BMI = 65 / (1.70²) = 22.5 (healthy). Healthy weight range for 1.70 m is 53.5–72.0 kg (BMI 18.5–24.9).
Rounding: We show 1 decimal place by default (you can change it).
BMI Chart for Adults (Age 18+)
The healthy BMI range can vary slightly by age group. The chart below provides a general reference for adult men and women.
Age Group | Underweight | Healthy Weight | Overweight | Obese |
|---|---|---|---|---|
18–24 years | < 19 | 19 – 24 | 25 – 29 | > 29 |
25–34 years | < 20 | 20 – 25 | 26 – 30 | > 30 |
35–44 years | < 21 | 21 – 26 | 27 – 31 | > 31 |
45–54 years | < 22 | 22 – 27 | 28 – 32 | > 32 |
55–64 years | < 23 | 23 – 28 | 29 – 33 | > 33 |
65+ years | < 24 | 24 – 29 | 30 – 34 | > 34 |
BMI Categories (Standard WHO Classification)
Category | BMI Range |
|---|---|
Underweight | < 18.5 |
Healthy Weight | 18.5 – 24.9 |
Overweight | 25 – 29.9 |
Obesity | 30+ |
🍏 Health Guidance Based on BMI Category
If You Are Underweight (BMI < 18.5)
Being underweight can indicate nutritional deficiencies or underlying medical issues.
Possible reasons include:
- High metabolism
- Low calorie intake or eating disorders
- Chronic illness or medical conditions
Recommended next steps:
- Increase high-nutrient foods like nuts, oats, dried fruits, eggs, and dairy
- Add strength training to build muscle mass
- Speak to a doctor or dietitian if weight loss is unexplained
- Try our Calorie Calculator to help increase healthy calorie intake
If You Have a Healthy BMI (18.5 – 24.9)
You are within the recommended range for most adults.
What to do next:
- Maintain balanced nutrition
- Exercise 150–300 minutes weekly
- Monitor weight every few months
If You Are Overweight (BMI 25 – 29.9)
This range indicates increased risk of heart disease, diabetes, and blood pressure issues.
Suggested actions:
- Reduce calorie-dense processed foods
- Walk or exercise regularly
- Track and monitor weight changes
If You Are Obese (BMI 30+)
A high BMI significantly increases risk of serious health problems.
Health guidance:
- Consider structured weight-loss plans
- Consult with a healthcare professional
- Combine diet changes + exercise for long-term results
💪 BMI Limitations & Accuracy
BMI is a useful general health indicator, but it is not perfect. It was created as a population-level statistical tool and does not measure body fat directly.
BMI may not be accurate for:
- Athletes or muscular individuals
- Pregnant or breastfeeding women
- People with very low muscle mass
- Children and teenagers under 18
Better alternatives to consider:
- Body fat percentage
- Waist-to-height ratio
- Medical assessment
👶 BMI for Children & Teenagers
For children and teens (ages 2-18), BMI is calculated differently. Instead of fixed numbers, doctors use percentile charts that compare children to others of the same age and sex.
Example:
Category | Percentile |
|---|---|
Underweight | < 5th percentile |
Healthy Weight | 5th – 85th percentile |
Overweight | 85th – 95th percentile |
Obese | > 95th percentile |
If you are checking BMI for a child, use a pediatric BMI calculator and consult a healthcare professional.
BMI – FAQs
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Information on this page is for education only and is not a substitute for professional medical advice.