BMI Calculator
BMI = kg/m² ()
- Healthy BMI range: 18.5 kg/m² – 25 kg/m²
- Healthy weight for the height:
- BMI Prime:
- Ponderal Index: kg/m³
What is BMI?
BMI stands for Body Mass Index. It is a simple number used to check whether a person’s weight is healthy for their height.
BMI is calculated using your height and weight. It does not measure body fat directly, but it gives a quick idea about weight status.
BMI Categories
- Underweight: BMI less than 18.5
- Normal weight: BMI 18.5 – 24.9
- Overweight: BMI 25 – 29.9
- Obesity: BMI 30 or more
Why is BMI Used?
BMI is used by doctors and health professionals to:
- Screen for underweight, overweight, and obesity
- Check risk of diabetes, heart disease, and blood pressure
- Monitor weight changes over time
- Give general health advice
Important Medical Note
BMI is a screening tool, not a diagnosis. It does not consider muscle mass, bone density, or body fat.
For athletes, pregnant women, elderly people, and people with medical conditions, BMI results should be reviewed by a doctor.
Always consult a healthcare professional for a complete health assessment.
BMI Formula and How to Use
BMI Formula (Metric)
BMI Formula (US)
How to Use BMI
- Measure your height and weight
- Apply the BMI formula
- Get your BMI number
- Compare it with the BMI chart
BMI Categories (Adults)
- Below 18.5 – Underweight
- 18.5 to 24.9 – Normal
- 25 to 29.9 – Overweight
- 30 or more – Obesity
BMI is for general guidance only. Always consult a doctor for medical advice.
BMI Chart for Children (Ages 2–19 Years)
| BMI Percentile | Weight Status | Meaning |
|---|---|---|
| Below 5th percentile | Underweight | Child has very low body weight |
| 5th – 84th percentile | Healthy weight | Child has healthy growth |
| 85th – 94th percentile | Overweight | Child weighs more than normal |
| 95th percentile or above | Obese | High risk, medical advice needed |
BMI for children is based on age and gender. Always consult a pediatrician for correct interpretation.
BMI Chart (Adults)
| BMI Value | Category | Meaning |
|---|---|---|
| Below 16.0 | Severe Underweight | Very low body weight |
| 16.0 – 18.4 | Underweight | Low body weight |
| 18.5 – 24.9 | Normal | Healthy body weight |
| 25.0 – 29.9 | Overweight | Higher than normal weight |
| 30.0 – 34.9 | Obesity Class I | Moderate obesity |
| 35.0 – 39.9 | Obesity Class II | Severe obesity |
| 40.0 and above | Obesity Class III | Very severe obesity |
BMI is used for adults (18+ years). It does not measure body fat directly.
Why BMI Chart is Used
The BMI chart helps to understand whether a person’s body weight is healthy for their height.
- To identify underweight, normal weight, overweight, and obesity
- To find early risk of health problems
- To monitor growth in children
- To guide diet and lifestyle changes
- To track weight changes over time
BMI chart is a screening tool only. Always consult a doctor for medical advice.
Risks of Being Underweight
Being underweight can cause health problems, such as:
- Poor nutrition, lack of vitamins, and anemia (low red blood cells)
- Weak bones (osteoporosis), which can break easily
- Weak immune system, so you get sick more often
- Growth and development problems in children and teenagers
- Hormone problems in women, which can cause missed periods
- Higher risk of miscarriage in underweight women
- More problems after surgery
- Higher risk of death compared to people with healthy weight
- Sometimes, being underweight is a sign of a disease, like anorexia nervosa
Risks of Being Overweight
Being overweight increases the risk of many serious diseases and health problems. According to the CDC, the risks include:
- High blood pressure
- High bad cholesterol (LDL), low good cholesterol (HDL), and high triglycerides
- Type 2 diabetes
- Heart disease
- Stroke
- Gallbladder disease
- Osteoarthritis (joint pain due to cartilage damage)
- Sleep apnea and breathing problems
- Certain cancers (breast, colon, kidney, liver, and others)
- Poor quality of life
- Mental health problems such as depression and anxiety
- Body pain and difficulty with physical activities
- Higher risk of death compared to people with healthy weight
Being overweight can lead to serious and sometimes life-threatening problems. It is usually advised to keep BMI below 25. Always talk to a doctor to know if lifestyle changes are needed.
Benefits of BMI Calculator
A BMI calculator is a simple tool used to check weight status based on height.
- Quick and easy to use
- Helps detect underweight or overweight
- Supports early health risk assessment
- Useful for doctors and health professionals
- Helps in diet and exercise planning
- Can be used to monitor weight over time
BMI calculator gives general guidance only. Medical advice should come from a healthcare professional.
Limitations of BMI
BMI (Body Mass Index) is a simple tool, but it does not show the full picture of health. Some limitations are listed below:
- BMI does not tell the difference between fat and muscle
- Muscular people may be labeled overweight or obese
- BMI does not show where fat is stored in the body
- It does not consider age or gender differences
- BMI does not measure body fat percentage
- It may not be accurate for athletes, elderly people, or children
- BMI does not consider bone density
- People with normal BMI can still have health problems
BMI should be used as a screening tool only. For better health assessment, talk to a doctor and consider other tests.
BMI Chart – Summary
BMI (Body Mass Index) is used to understand whether a person’s weight is healthy for their height.
Adults (18+ years)
- Below 18.5 – Underweight
- 18.5 to 24.9 – Normal (Healthy)
- 25 to 29.9 – Overweight
- 30 or more – Obesity
Children (2–19 years)
- Below 5th percentile – Underweight
- 5th to 84th percentile – Healthy weight
- 85th to 94th percentile – Overweight
- 95th percentile or above – Obese
BMI is a screening tool only. Always consult a doctor or pediatrician for correct health advice.