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Free BMI Calculator — Check Your Body Mass Index

Calculate your Body Mass Index (BMI) instantly by entering your height and weight. This calculator shows your BMI value, weight category (underweight, normal, overweight, or obese), and ideal weight range for your height — using both WHO international standards and Indian-specific thresholds. Supports kg/cm and lbs/ft units. All calculations run in your browser — your health data is never stored, sent, or shared with anyone.

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BMI categories based on WHO and Indian Council of Medical Research (ICMR) guidelines. Last updated: April 2026. This calculator is for informational screening only — consult a healthcare provider for medical advice.

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What is BMI? (Body Mass Index Explained)

BMI stands for Body Mass Index — a numerical value calculated from your weight and height that estimates whether your body weight is proportional to your height. It was devised by Belgian mathematician Adolphe Quetelet in the 1830s and adopted by the World Health Organization (WHO) as a standard screening tool for weight categories in adults.

BMI does not directly measure body fat. Instead, it serves as a quick, inexpensive screening metric that correlates with body fat levels at a population level. A high BMI suggests excess weight that may increase your risk of heart disease, type 2 diabetes, high blood pressure, and certain cancers. A low BMI may indicate nutritional deficiency, weakened immunity, or bone loss.

Key limitation: BMI cannot distinguish between muscle and fat. An athlete with high muscle mass may have an "overweight" BMI while being perfectly healthy. Similarly, an older adult with low muscle mass may have a "normal" BMI while carrying excess fat. BMI is a starting point — not a diagnosis. Combine it with waist circumference, body fat percentage, and clinical assessment for a complete picture.

BMI Categories: WHO and Indian Standards

WHO international BMI classification (adults 20+)

BMI range Category Health risk
Below 18.5 Underweight Nutritional deficiency, weakened immunity, osteoporosis
18.5 – 24.9 Normal weight Low risk — healthy range for most adults
25.0 – 29.9 Overweight Increased risk of cardiovascular disease, type 2 diabetes
30.0 – 34.9 Obese (Class I) High risk of metabolic syndrome, joint problems
35.0 – 39.9 Obese (Class II) Very high risk — medical intervention recommended
40.0 and above Obese (Class III) Extremely high risk — also called morbid obesity

Indian BMI thresholds (why they differ)

Research shows that South Asians develop metabolic complications at lower BMI values than Western populations. Indians tend to have higher body fat percentages and more abdominal (visceral) fat at the same BMI compared to Europeans. Based on this, Indian health guidelines suggest stricter thresholds:

BMI range Category (Indian standard) Action
Below 18.5 Underweight Evaluate nutrition, rule out underlying conditions
18.5 – 22.9 Normal weight Maintain with balanced diet and regular exercise
23.0 – 24.9 Overweight (at risk) Lifestyle modification, increase physical activity
25.0 and above Obese Medical consultation recommended, screen for diabetes and hypertension

Notice: the Indian "overweight" threshold starts at 23.0, not 25.0 as in WHO guidelines. An Indian adult with BMI 24 is already at elevated risk — even though WHO standards would classify them as "normal." If you are of South Asian descent, use the Indian thresholds for a more accurate risk assessment.

The BMI Formula

Metric formula (kg and cm)

BMI = Weight (kg) ÷ Height (m)<sup>2</sup>

Imperial formula (lbs and inches)

BMI = (Weight (lbs) ÷ Height (in)<sup>2</sup>) × 703

Worked example

A person who is 170 cm tall and weighs 72 kg:

  • Height in meters: 170 ÷ 100 = 1.70 m
  • Height squared: 1.70 × 1.70 = 2.89
  • BMI = 72 ÷ 2.89 = 24.9

By WHO standards, 24.9 is at the upper boundary of "normal weight." By Indian standards, this person is already in the "overweight (at risk)" category (threshold: 23.0). This example illustrates why knowing which standard applies to you matters — especially for South Asian populations.

BMI Chart: Quick Reference for Common Heights

This chart shows the weight ranges corresponding to each BMI category for common Indian heights. Find your height and check which range your weight falls in:

Height Underweight (<18.5) Normal (18.5–24.9) Overweight (25–29.9) Obese (≥30)
150 cm (4'11") Below 42 kg 42–56 kg 56–67 kg Above 67 kg
155 cm (5'1") Below 44 kg 44–60 kg 60–72 kg Above 72 kg
160 cm (5'3") Below 47 kg 47–64 kg 64–77 kg Above 77 kg
165 cm (5'5") Below 50 kg 50–68 kg 68–81 kg Above 81 kg
170 cm (5'7") Below 53 kg 53–72 kg 72–87 kg Above 87 kg
175 cm (5'9") Below 57 kg 57–76 kg 76–92 kg Above 92 kg
180 cm (5'11") Below 60 kg 60–81 kg 81–97 kg Above 97 kg
185 cm (6'1") Below 63 kg 63–85 kg 85–102 kg Above 102 kg

Note: These ranges use WHO international standards. For Indian adults, the "overweight" threshold starts at BMI 23.0, meaning the normal weight upper limit would be approximately 2-3 kg lower for each height.

Limitations of BMI: What It Doesn't Tell You

BMI is a useful screening tool but has important blind spots. Understanding these helps you interpret your result correctly:

Muscle vs fat

BMI treats all weight equally — it cannot distinguish between muscle, fat, bone, and water. A muscular person (athlete, bodybuilder, manual laborer) may have a BMI of 28-30 while having low body fat. Conversely, a sedentary person with low muscle mass may have a "normal" BMI of 22 while carrying excess visceral fat. For body composition analysis, consider our Body Fat Calculator.

Fat distribution

Where you carry fat matters more than how much you weigh. Abdominal (visceral) fat around organs is far more dangerous than fat on hips or thighs. Two people with the same BMI can have very different health risks based on fat distribution. Waist circumference is a better predictor of metabolic risk than BMI alone: above 90 cm for Indian men and 80 cm for Indian women indicates elevated risk.

Age and gender

Older adults naturally lose muscle mass (sarcopenia), so the same BMI at age 65 represents more fat than at age 25. Women typically have 10-15% more body fat than men at the same BMI. The BMI formula doesn't account for either factor.

Ethnicity

South Asians, East Asians, and Pacific Islanders develop metabolic complications at different BMI thresholds than Europeans. This is why Indian guidelines use 23.0 as the overweight threshold rather than 25.0. Always use population-appropriate thresholds.

What to use alongside BMI

  • Waist circumference: Best single measure of abdominal fat risk
  • Body fat percentage: Via DEXA scan, bioimpedance, or calipers (estimate yours here)
  • Waist-to-hip ratio: Indicates fat distribution pattern
  • Blood tests: Fasting glucose, lipid panel, HbA1c reveal metabolic health regardless of BMI
  • Physical fitness: An "overweight" person who exercises regularly may be healthier than a "normal weight" sedentary person

How to Reach and Maintain a Healthy BMI

If your BMI is above normal (overweight or obese)

Weight loss is fundamentally about sustaining a calorie deficit — consuming fewer calories than your body uses. Use our Calorie/TDEE Calculator to find your maintenance calories, then aim for 300-500 calories below that for sustainable weight loss (0.25-0.5 kg per week). Crash diets (1,000+ calorie deficit) are counterproductive — they cause muscle loss, metabolic slowdown, and almost always lead to weight regain.

Combine dietary changes with resistance training (bodyweight exercises, gym, yoga) to preserve muscle while losing fat. Track progress using waist measurement rather than weight alone — the scale can be misleading when body composition changes.

If your BMI is below normal (underweight)

Being underweight can indicate insufficient nutrition, underlying medical conditions (thyroid issues, celiac disease), or disordered eating. Focus on calorie-dense, nutrient-rich foods rather than junk food. Strength training helps build muscle mass. If underweight persists despite dietary efforts, consult a healthcare provider to rule out medical causes.

If your BMI is in the normal range

Maintain with balanced nutrition and regular physical activity (150 minutes moderate exercise per week, per WHO guidelines). Check your BMI periodically — every 3-6 months is sufficient unless you're actively changing weight. Use our Macro Calculator for optimal protein/carb/fat ratios.

Frequently asked questions

What is BMI?

BMI is weight in kilograms divided by height in meters squared (kg/m²). It is a quick, inexpensive population-level screen for whether weight is broadly proportional to height, not a direct measure of body fat or fitness. When you switch between cm/ft-in or kg/lb, this calculator converts your entries so height and weight stay equivalent and your BMI updates correctly. Use BMI as a starting point alongside waist circumference, activity level, and clinical advice—not as a diagnosis by itself.

Does gender change the BMI number?

The BMI formula is the same numeric calculation for adult men and women. Optional gender on this page only adjusts short explanatory text; it does not change the BMI value. Women typically carry a higher body-fat percentage than men at the same BMI, so clinicians may interpret identical numbers differently in context. For sport-specific or pregnancy-related questions, rely on individualized medical guidance rather than BMI alone.

Is BMI accurate for Indians or South Asian populations?

BMI is useful for screening, but many Indian and South Asian guidelines recommend stricter action thresholds because cardiometabolic risk can rise at lower BMI values than in some Western populations. Waist circumference and family history of diabetes often matter as much as the BMI digit. Treat Indian cutoffs (for example overweight from BMI 23) as an additional lens alongside WHO ranges. A qualified clinician can help you interpret results for your personal history.

What about body fat percentage?

Body fat percentage estimates how much of your mass is fat versus lean tissue—DEXA, skinfold calipers, and bioimpedance scales each have measurement error and cost trade-offs. BMI is faster and cheaper but cannot separate muscle from fat, which is why athletes may look “overweight” on BMI while being lean. For a practical estimate from measurements, try our Body Fat Calculator alongside BMI for a fuller picture.

Why is the meter needle clipped at extremes?

Very high or very low BMI values are mapped to the ends of the colored bar so the needle remains visible on phones and small screens. The numeric BMI value above the gauge is always the full calculated result; only the visual position is clamped for readability. If your BMI is far outside the common adult range, rely on the number and category text rather than the needle position alone. Discuss extreme values with a healthcare provider.

What is a healthy BMI for Indian adults?

By Indian-specific guidelines, a healthy BMI for adults is 18.5 to 22.9. This is lower than the WHO international range of 18.5 to 24.9 because South Asians develop metabolic complications (diabetes, heart disease) at lower BMI values. An Indian adult with BMI 24 is already at elevated risk, even though WHO standards classify this as "normal." If you are of South Asian descent, use the Indian threshold of 23.0 as your overweight marker.

How do I calculate my BMI manually?

Divide your weight in kilograms by your height in meters squared. For example, if you weigh 68 kg and are 165 cm (1.65 m) tall: BMI = 68 ÷ (1.65 × 1.65) = 68 ÷ 2.72 = 25.0. For imperial units: multiply weight in pounds by 703, then divide by height in inches squared. Or simply use the calculator above — it handles the math instantly.

Is BMI the same for men and women?

The BMI formula is identical for both. However, women naturally carry 10-15% more body fat than men at the same BMI, meaning a BMI of 24 represents different body compositions in men versus women. The WHO does not differentiate BMI categories by gender, but clinicians consider gender alongside BMI when assessing health risk. For more precise body composition, use our Body Fat Calculator.

What BMI is considered obese?

By WHO standards, a BMI of 30.0 or higher is classified as obese. This is further divided into Class I (30-34.9), Class II (35-39.9), and Class III or morbid obesity (40+). For Indian adults, the obesity threshold is lower at BMI 25.0 because South Asians face higher metabolic risks at lower weights. If your BMI is 30+, consult a healthcare provider for a comprehensive health assessment.

Is this BMI calculator private? Where is my data stored?

Your data is not stored anywhere. This calculator runs entirely in your browser — no health information (height, weight, BMI result) is sent to any server, database, or third party. When you close the tab, everything disappears. Unlike many health calculators that feed data to insurance companies or advertising platforms, DoItSwift has no tracking, no account creation, and no data collection.

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