BMI (Body Mass Index) is a number calculated from your height and weight. It was developed by Belgian mathematician Adolphe Quetelet in the 1830s and was adopted by the WHO as a health screening tool in the 1980s. It gives a quick estimate of whether someone is underweight, healthy weight, overweight or obese — based on population-level data.
BMI is a screening tool, not a diagnostic tool. A high or low BMI should prompt further evaluation, not a diagnosis by itself.
Imperial and metric · Healthy weight range · BMI category with health guidance.
Open BMI Calculator →| BMI Range | Category | Health Risk |
|---|---|---|
| Below 18.5 | Underweight | Malnutrition, bone density loss, immune problems |
| 18.5 – 24.9 | Normal Weight | Lowest risk — healthy range |
| 25.0 – 29.9 | Overweight | Increased risk of cardiovascular disease |
| 30.0 – 34.9 | Obese Class I | High risk — diabetes, heart disease, hypertension |
| 35.0 – 39.9 | Obese Class II | Very high risk — severe health complications |
| 40.0 and above | Obese Class III | Extremely high risk — life threatening |
What does a "normal" BMI (18.5–24.9) look like in actual pounds and kilograms?
| Height | Healthy Weight Range (BMI 18.5–24.9) | Overweight Starts At |
|---|---|---|
| 5'0" (152 cm) | 95–128 lbs (43–58 kg) | 128+ lbs |
| 5'3" (160 cm) | 107–141 lbs (49–64 kg) | 141+ lbs |
| 5'6" (168 cm) | 118–155 lbs (54–70 kg) | 155+ lbs |
| 5'9" (175 cm) | 125–169 lbs (57–77 kg) | 169+ lbs |
| 6'0" (183 cm) | 140–183 lbs (64–83 kg) | 183+ lbs |
| 6'3" (190 cm) | 152–200 lbs (69–91 kg) | 200+ lbs |
The standard WHO BMI categories (18.5–24.9 normal) apply to both men and women. However, the same BMI can represent different body compositions between sexes:
The practical implication: BMI is a reasonable population-level tool but may not perfectly reflect an individual's health status regardless of sex.
The WHO and many Asian health authorities recognize that people of Asian descent tend to have higher body fat percentage at the same BMI compared to Caucasian populations. Several Asian countries use modified BMI thresholds:
| Category | Standard WHO BMI | Asian-Specific BMI |
|---|---|---|
| Underweight | < 18.5 | < 18.5 |
| Normal | 18.5–24.9 | 18.5–22.9 |
| Overweight | 25.0–29.9 | 23.0–27.4 |
| Obese | 30.0+ | 27.5+ |
For Indian, Chinese, Japanese and other South/East Asian populations, a BMI of 23+ may already carry increased health risks typically associated with the overweight category in Western standards.
1. Muscle vs Fat: A muscular athlete can have a BMI of 28 (overweight) with very low body fat. 2. Age: Older adults naturally have less muscle — the same BMI carries different health implications. 3. Ethnicity: Different populations have different body compositions at the same BMI. 4. Height extremes: BMI overestimates obesity risk in very tall people and underestimates it in very short people. 5. Fat distribution: Where you carry fat (belly vs hips) matters as much as how much — BMI ignores this entirely.
| Metric | What It Measures | Healthy Range | Better Than BMI For |
|---|---|---|---|
| Waist Circumference | Abdominal fat | <35" women, <40" men | Cardiovascular risk |
| Waist-to-Hip Ratio | Fat distribution | <0.85 women, <0.90 men | Metabolic risk |
| Body Fat % | Actual fat vs lean mass | 21–33% women, 8–19% men | Athletes, muscle mass |
| Waist-to-Height Ratio | Central obesity | Below 0.5 | Overall health prediction |
A simple rule gaining acceptance in research: your waist circumference should be less than half your height. If you're 5'9" (69 inches), your waist should be under 34.5 inches. This single measurement predicts cardiovascular and metabolic risk better than BMI alone and takes only seconds to calculate.
| Country | Average BMI (Men) | Average BMI (Women) | Category |
|---|---|---|---|
| United States | 29.5 | 30.0 | Overweight / Obese I |
| United Kingdom | 27.4 | 27.1 | Overweight |
| India | 22.5 | 22.2 | Normal |
| Japan | 23.7 | 22.3 | Normal |
| China | 24.0 | 23.2 | Normal |
| Australia | 27.2 | 27.0 | Overweight |
Imperial and metric · Healthy weight range · BMI category · Body weight guidance.
Check My BMI →The WHO defines a healthy BMI range as 18.5 to 24.9 for adults of all ages. Below 18.5 is underweight, 25–29.9 is overweight, and 30 or above is obese. For Asian populations, many health authorities recommend a lower threshold of 23 for overweight and 27.5 for obese due to higher cardiovascular risk at lower BMI values.
By WHO standards, BMI 25.0 is the start of the overweight category. However, this doesn't mean you are unhealthy at 25.0. BMI is a screening tool, not a diagnosis. A muscular person with very low body fat can easily have a BMI of 25–27 and be in excellent health. If your BMI is 25, talk to your doctor about other metrics like waist circumference and body fat percentage for a more complete picture.
The healthy BMI range for adult women is the same as men — 18.5 to 24.9 by WHO standards. However, women naturally carry more essential body fat than men, so body fat percentage tells a more nuanced story. Healthy body fat for women is 21–33%, compared to 8–19% for men. A woman with BMI 22 may be perfectly healthy even though her body fat is higher than a man with the same BMI.
Yes — BMI can significantly misclassify individuals. Athletes and very muscular people often have BMIs in the overweight range despite having low body fat and excellent health. Conversely, people with "normal" BMI can have high body fat percentages (called "skinny fat" or normal-weight obesity), which carries real health risks that BMI misses. Use BMI as a starting point, not a final assessment.
For people of South Asian descent including Indians, health authorities recommend a lower BMI threshold due to higher risk of metabolic diseases at lower BMI values. The suggested healthy range for Indians is 18.5–22.9, with 23–27.4 considered overweight and 27.5+ considered obese. This is more conservative than WHO standards because South Asians tend to have higher body fat percentage and visceral fat at the same BMI compared to Western populations.