How BMI is Measured
and What It Means

What is BMI?

What Is Body Mass Index and How Is BMI Measured?

BMI — or Body Mass Index — is measured by dividing your weight in kilograms by the square of your height in metres. It gives you a single number that indicates whether you are underweight, normal weight, overweight, or obese. For Indians and South Asians, the healthy range is different from Western standards — and understanding why can change how you interpret your results.

BMI stands for Body Mass Index. It is a simple numerical value calculated from your height and weight. It was first developed by Belgian mathematician Adolphe Quetelet in the 1830s and was later adopted by the World Health Organization (WHO) as a standard screening tool for population-level obesity.

BMI does not directly measure body fat. Instead, it uses weight relative to height as an indirect estimate of whether your body weight is appropriate for your height. It is free, requires no equipment, and takes seconds to calculate, which is why it remains the most widely used health screening tool in the world.

The term "Body Mass Index" was coined by Ancel Keys in 1972, who recommended it for use in population studies — not as an individual diagnostic tool. This distinction is important: BMI was designed to study trends across large groups, not to make precise individual health assessments. Understanding this helps you interpret your own result in the right context.

The Formula

How Is BMI Measured? The Formula Explained

BMI is calculated using one simple formula. There are two versions — one for the metric system and one for imperial measurements:

Example Calculation

Let's say you weigh 72 kg and your height is 1.68 m:

1. Square your height: 1.68 × 1.68 = 2.8224
2. Divide weight by that number: 72 ÷ 2.8224 = 25.5
3. Your BMI is 25.5 — which in Indian cutoffs falls in the overweight category

You do not need to do this manually. Use the free BMI Calculator on DialFit to get your result instantly, along with your ideal weight range and personalised interpretation.

BMI Categories

What Does Your BMI Number Mean?

Once you have your BMI number, you compare it against a reference range. There are two sets of cutoffs — global (WHO) cutoffs and Asian/Indian cutoffs. Here is the comparison:

Indian Context

Why Indian BMI Cutoffs Are Different

The standard WHO BMI cutoffs were developed using data from European and North American populations. Indians and South Asians have a different body composition — higher body fat percentage at the same BMI, and a tendency to accumulate fat around the abdomen rather than the limbs.

The WHO and Indian research studies both support using lower cutoffs for South Asian populations. This is why the DialFit BMI Calculator applies Indian cutoffs by default — so your result is actually relevant to your body.

Limitations

Limitations of BMI — What It Does Not Tell You

BMI is a useful starting point, but it has real limitations you should be aware of:

• It does not distinguish muscle from fat. A bodybuilder with very low body fat may have a BMI of 28 — classified as overweight — because muscle is heavy. Their metabolic health may be excellent despite the high BMI number.
• It ignores where fat is stored. Abdominal fat is far more dangerous than fat stored in the hips or thighs, but BMI does not capture this. Two people with the same BMI can have completely different fat distributions — and completely different health risks.
• It does not account for age. Older adults naturally lose muscle mass, so a normal BMI can still coexist with excess body fat in people over 60. This is called "sarcopenic obesity" — a condition where BMI appears normal but body fat is high and muscle mass is dangerously low.
• It differs by gender. Women naturally carry more body fat than men at the same BMI — BMI does not adjust for this. A woman and a man with identical BMI values will typically have very different body compositions.
• It does not reflect fitness level. A sedentary person and an active person can have the same BMI yet have dramatically different cardiovascular fitness, insulin sensitivity, and long-term health outcomes.

Despite these limitations, BMI remains a valuable first screening tool. Its strength is in its simplicity — it requires no equipment and produces a result in seconds. For a more complete picture of your health, use BMI together with your Waist-to-Hip Ratio, Body Fat Percentage, and consider checking your Diabetes Risk — especially if your BMI is above 23.

Taking Action

How to Use Your BMI Result

Your BMI number alone should not drive major health decisions. Here is how to use it sensibly:

If your BMI is below 18.5 (Underweight)

Focus on nutrient-dense foods and adequate protein. Underweight can indicate insufficient calorie intake, malnutrition, or an underlying medical condition. Use the Protein Calculator to find your daily protein target and the Build My Plate tool to plan balanced meals. Consult a doctor if you are losing weight unintentionally — unexplained weight loss is always worth investigating.

If your BMI is 18.5–22.9 (Normal for Indians)

You are in the healthy range. The priority is maintenance — a balanced diet, regular physical activity, and annual health checks. Even within the normal range, it is worth checking your waist circumference. Indian men with a waist above 90 cm and Indian women above 80 cm face elevated metabolic risk even at a normal BMI. Consider using the Health Analyzer for a complete overview of your health metrics.

If your BMI is 23–24.9 (Overweight for Indians)

This is a risk zone, especially for Indians. Even a 5% reduction in body weight significantly improves metabolic health markers — blood sugar, blood pressure, and cholesterol all tend to improve with modest weight loss. Calculate your TDEE and use the Weight Loss Calculator to set a sustainable calorie deficit of 300–500 kcal per day.

If your BMI is 25 and above (Obese for Indians)

At this level, the risk of type 2 diabetes, high blood pressure, and cardiovascular disease increases substantially. Research shows that Indians develop these conditions at lower BMI thresholds than Western populations — so a BMI above 25 warrants prompt attention. Professional support from a doctor or dietitian is strongly recommended. Talk to a DialFit expert — our volunteer dietitians can create a personalised plan for you, at no cost.

Comparison

BMI vs Other Body Composition Measures

BMI is best used alongside other measurements. Here is a quick comparison:

Using all four together gives you a far more accurate picture of your health than BMI alone. All of these are available for free on DialFit.

A practical example: consider an Indian man with a BMI of 24 — within the normal range for Western standards, but borderline overweight by Indian cutoffs. If his waist circumference is 92 cm (above the 90 cm threshold for Indian men) and his body fat percentage is 27% (above the 25% obesity cutoff for men), he faces significant metabolic risk despite a "normal" BMI. Checking all four metrics together reveals the full picture that BMI alone would miss.

This is precisely why DialFit provides all these tools in one place — so you can build a complete picture of your health in minutes, not months. Start with BMI, then layer in body fat percentage and waist-hip ratio for a comprehensive health assessment that is genuinely relevant to Indians.

Common Questions

Frequently Asked Questions