BMI Calculator – Calculate Body Mass Index Online
BMI Calculator
BMI Breakdown
| BMI Range | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Normal Weight |
| 25 – 29.9 | Overweight |
| 30 and Above | Obese |
What is BMI?
BMI, or Body Mass Index, is a simple numerical measure calculated from a person's weight and height. It is widely used by doctors, dietitians, and health professionals as a quick screening tool to classify whether an individual falls into the underweight, normal weight, overweight, or obese category. While BMI does not directly measure body fat, it correlates well with more precise measures of body composition and is a reliable first indicator of weight-related health risks.
The World Health Organization (WHO) and the Indian Council of Medical Research (ICMR) both use BMI as a standard population-level health metric. For most adults aged 18 and above, BMI provides a fast and cost-free way to assess whether your current weight puts you at risk for conditions like type 2 diabetes, heart disease, hypertension, or joint problems.
How to Use This BMI Calculator
- Enter your weight in kilograms (kg).
- Enter your height in centimetres (cm).
- Click Calculate BMI.
- Your BMI value, category, and healthy weight range will be displayed instantly.
BMI Formula
BMI = Weight (kg) ÷ Height (m)²
Example: A person weighing 70 kg with a height of 175 cm (1.75 m):
- Height in metres = 175 ÷ 100 = 1.75 m
- BMI = 70 ÷ (1.75 × 1.75) = 70 ÷ 3.0625 = 22.86
- Category: Normal Weight
BMI Categories (WHO Standard)
| BMI Range | Category | Health Risk |
|---|---|---|
| Below 18.5 | Underweight | Risk of malnutrition, anaemia, weak immunity |
| 18.5 – 24.9 | Normal Weight | Low risk — healthy range |
| 25.0 – 29.9 | Overweight | Moderate risk of heart disease, diabetes |
| 30.0 – 34.9 | Obese (Class I) | High risk — lifestyle intervention needed |
| 35.0 – 39.9 | Obese (Class II) | Very high risk |
| 40 and above | Severely Obese (Class III) | Extremely high risk — medical attention required |
Note for Indian adults: Research suggests that Asian populations including Indians face higher health risks at lower BMI thresholds. Many Indian health guidelines recommend considering overweight at BMI ≥ 23 and obesity at BMI ≥ 25, rather than the standard WHO cutoffs of 25 and 30.
Healthy Weight Range by Height
| Height (cm) | Healthy Weight Range (kg) |
|---|---|
| 150 cm | 41.6 – 56.0 kg |
| 155 cm | 44.4 – 59.9 kg |
| 160 cm | 47.4 – 63.7 kg |
| 165 cm | 50.3 – 67.7 kg |
| 170 cm | 53.5 – 71.9 kg |
| 175 cm | 56.7 – 76.3 kg |
| 180 cm | 59.9 – 80.7 kg |
Limitations of BMI
- Does not measure body fat directly: A muscular athlete may have a high BMI but very low body fat — BMI would incorrectly classify them as overweight.
- Does not account for fat distribution: Abdominal fat (visceral fat) is more dangerous than fat stored in the hips or thighs, and BMI cannot distinguish between the two.
- Not suitable for children: For individuals under 18, age- and gender-specific BMI percentile charts should be used instead.
- Not applicable during pregnancy: BMI is not a useful measure for pregnant women.
- Ethnic variation: Health risks at a given BMI level differ across ethnic groups — Indians and other Asians are at higher risk at lower BMI values than Europeans.
Frequently Asked Questions (FAQs)
What is a normal BMI range?
For most adults, a BMI between 18.5 and 24.9 is considered normal or healthy. However, for Indian adults, many health guidelines suggest that a BMI of 23 or above may already indicate increased health risk, and a BMI of 25 or above may be considered obese in the Indian context.
How is BMI calculated?
BMI is calculated by dividing your weight in kilograms by the square of your height in metres. The formula is: BMI = Weight (kg) ÷ Height (m)². For example, if you weigh 65 kg and are 1.68 m tall, your BMI = 65 ÷ (1.68)² = 65 ÷ 2.82 = 23.0.
What if my BMI is too high?
A BMI above 25 (or above 23 for Indians) suggests you may be carrying excess weight that could increase health risks. The recommended steps include consulting a doctor or registered dietitian, adopting a calorie-controlled diet, and increasing physical activity. Gradual, steady weight loss of 0.5–1 kg per week is the healthiest approach.
What if my BMI is too low?
A BMI below 18.5 indicates underweight, which can be associated with nutritional deficiencies, weak immunity, bone density loss, and anaemia. If your BMI is below this range, consult a doctor or nutritionist to rule out underlying conditions and develop a plan to reach a healthy weight through a nutrient-rich diet.
Is BMI accurate for Indians?
Standard BMI cutoffs were developed primarily on Western populations. Research consistently shows that Indians and other South Asians develop metabolic conditions such as type 2 diabetes and heart disease at lower BMI levels. The Indian Consensus Group recommends considering overweight at BMI ≥ 23 and obesity at BMI ≥ 25 for the Indian population specifically.
Can children use this BMI calculator?
This calculator is designed for adults aged 18 and above. For children and teenagers, BMI interpretation requires age- and gender-specific growth charts (BMI-for-age percentiles) because body fat levels change significantly during growth and development. Please consult a paediatrician for weight assessment in children.