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BMI Calculator

Calculate Body Mass Index with metric or imperial units.

How to calculate BMI

BMI = weight in kilograms ÷ (height in meters)². For example, a person weighing 70 kg at 1.75 m height has a BMI of 70 ÷ (1.75 × 1.75) = 22.9, which falls in the Normal weight range.

In imperial units: BMI = (weight in lbs × 703) ÷ (height in inches)².

BMI categories (WHO, adults 20+)

  • Under 18.5 — Underweight
  • 18.5 – 24.9 — Normal weight
  • 25 – 29.9 — Overweight
  • 30 – 34.9 — Obese (Class I)
  • 35 – 39.9 — Obese (Class II)
  • 40+ — Obese (Class III)

Limitations of BMI

BMI is a population-level screening tool, not a personal health verdict. A bodybuilder with high muscle mass may register "overweight" despite low body fat. An older adult with low muscle mass may show "normal" BMI despite high body fat. Use BMI as one data point — not the only one.

BMI for Indian adults

Research consistently shows that South Asians, including Indians, develop metabolic risk factors (type 2 diabetes, cardiovascular disease) at lower BMI values than Western populations. The WHO Asian cut-offs suggest overweight begins at BMI ≥23 and obesity at ≥27.5 for Asian populations. Several Indian health organisations and ICMR guidelines recommend using these lower thresholds for clinical decisions, although the international WHO thresholds (25 and 30) are still used on this calculator as the globally accepted standard.

Who uses this BMI calculator

Individuals use it as a quick health screening check before a doctor's visit. Fitness coaches use it to set baseline metrics for new clients. Dietitians use it to document starting points and track progress. Corporate wellness programmes include BMI checks in annual health screenings. Insurance companies in India use BMI as one factor in health and life insurance premium calculations — a higher BMI category may lead to higher premiums or additional medical tests.

Healthy weight range

This calculator also shows your healthy weight range — the weight span that would put you in the 18.5–24.9 BMI bracket for your height. For a person 170 cm tall, the healthy range is approximately 53–72 kg. This range gives you a practical target if you are working with a doctor or nutritionist toward a weight goal.

Frequently asked questions

What is BMI?
BMI (Body Mass Index) is a number calculated from your weight and height. It's used screening tool to identify possible weight-related health risks. BMI = weight (kg) ÷ height² (m). It doesn't directly measure body fat but correlates with body fat levels in most adults.
What are the BMI categories?
Under 18.5: Underweight. 18.5–24.9: Normal weight. 25–29.9: Overweight. 30–34.9: Obese Class I. 35–39.9: Obese Class II. 40+: Obese Class III. These are WHO classifications for adults aged 20 and older.
Is BMI accurate?
BMI is a screening tool, not a diagnostic one. It h limitations: it doesn't distinguish between muscle and fat (athletes may show 'overweight' BMI), it doesn't account for age, sex, or ethnicity differences in body composition, and it can underestimate body fat in older adults. Consult a doctor for a full health assessment.
Does BMI apply to children?
Children and teens use age- and sex-specific BMI-for-age percentiles rather than the adult cutoffs. This calculator is for adults (20+) only.
What is a healthy BMI for Indians?
Research suggests Indians and other South Asians may have higher health risks at lower BMI thresholds than Western populations. Some Indian health guidelines recommend a normal range of 18–22.9 and flag overweight at ≥23. The WHO cutoffs used here are the international standard.

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