Free BMI Calculator โ Instant Body Mass Index Results
Body Mass Index โ a measure of body fat based on height and weight
<18.5 Normal
18.5โ25 Overweight
25โ30 Obese
>30
BMI Categories (WHO)
| Category | BMI Range |
|---|---|
| Underweight | < 18.5 |
| Normal weight | 18.5 โ 24.9 |
| Overweight | 25 โ 29.9 |
| Obese Class I | 30 โ 34.9 |
| Obese Class II | 35 โ 39.9 |
| Obese Class III | โฅ 40 |
How to Calculate BMI Without Signing Up
Enter your height and weight above for instant results. Our free BMI calculator uses the standard formula (weight รท heightยฒ) with no account creation or personal data collection required.
What Is a Healthy BMI Range?
A BMI between 18.5 and 24.9 is classified as "Normal weight" by the WHO. Below 18.5 is underweight, 25โ29.9 is overweight, and 30+ is obese. Your ideal weight depends on height, age, and body composition.
Is BMI Accurate for Everyone?
BMI is a useful screening tool but has limitations. It doesn't distinguish between muscle and fat, so athletes may show a high BMI despite being healthy. Always consult a healthcare professional for personalized advice.
Obesity & Disease: What the Research Shows
A BMI of 30 or above is classified as obese. Research consistently links obesity to a significantly higher risk of several serious conditions.
Type 2 Diabetes
Obesity is the single strongest risk factor for Type 2 diabetes. Excess body fat, particularly around the abdomen, causes insulin resistance โ where cells stop responding effectively to insulin. People with a BMI over 30 are approximately 7 times more likely to develop Type 2 diabetes compared to those with a healthy BMI. Losing just 5โ10% of body weight can significantly improve insulin sensitivity.
Cardiovascular Disease (Heart Disease)
Obesity increases the risk of coronary artery disease, heart attack, and heart failure. Excess weight raises blood pressure, increases LDL ("bad") cholesterol, lowers HDL ("good") cholesterol, and promotes chronic inflammation โ all of which damage blood vessels over time. A BMI over 30 is associated with a 28% increased risk of cardiovascular disease.
Stroke
Obesity contributes to high blood pressure and atherosclerosis (hardening of arteries), both major causes of stroke. For every 5-unit increase in BMI above 25, stroke risk increases by approximately 18%.
Other Linked Conditions
- Sleep apnoea โ excess tissue around the airway causes breathing interruptions during sleep
- Certain cancers โ including breast, colon, kidney, and pancreatic cancer
- Osteoarthritis โ extra weight places stress on joints, especially knees and hips
- Fatty liver disease โ fat accumulation in the liver can lead to inflammation and scarring
- Mental health โ higher rates of depression and anxiety linked to obesity
โ ๏ธ Important: BMI is a screening tool, not a diagnostic one. It does not account for muscle mass, bone density, age, sex, or ethnic background. Consult a healthcare professional for personalised health advice.