BMI Calculator

Calculate your Body Mass Index instantly — find your weight category, healthy weight range, and personalised guidance.

Unit System

Height (cm)

Weight (kg)

Your BMI Result

Enter your height and weight, then click Calculate.

BMI Classification Table

BMI Range	Category	Health Risk
< 18.5	Underweight	Malnutrition, osteoporosis
18.5 – 24.9	Normal Weight	Lowest risk
25.0 – 29.9	Overweight	Moderate risk
30.0 – 34.9	Obese Class I	High risk
35.0 – 39.9	Obese Class II	Very high risk
≥ 40.0	Obese Class III	Extremely high risk

Frequently Asked Questions

BMI (Body Mass Index) measures body fat based on height and weight. Formula: BMI = weight (kg) ÷ height² (m²). For imperial: BMI = (weight in lbs × 703) ÷ height² (inches). It was developed by Adolphe Quetelet in the 1830s.

BMI is a useful screening tool but doesn't account for muscle mass, bone density, or fat distribution. Athletes may show a high BMI due to muscle. Older adults may have a "normal" BMI with excess body fat. Always consult a doctor for a full health assessment.

For adults aged 18–65, the WHO considers a BMI of 18.5 to 24.9 healthy. Below 18.5 is underweight; 25–29.9 is overweight; 30+ is obese. For Asian populations, the WHO suggests lower thresholds (overweight at 23, obese at 27.5).

Healthy weight range = 18.5 × height² to 24.9 × height² (height in metres). For example, at 170 cm: 53.5 kg – 72.0 kg. This calculator shows your personal range automatically after calculating.

For children and teenagers (2–19), BMI is interpreted using age- and sex-specific percentiles, not fixed cutoffs. A healthy BMI percentile is between the 5th and 85th. This calculator is designed for adults — use CDC BMI-for-age charts for children.

BMI uses only height and weight, so it cannot distinguish between muscle mass and fat mass. Muscle is denser and heavier than fat, meaning a highly muscular athlete may register as "overweight" or even "obese" on the BMI scale despite having very low body fat. For athletes, body fat percentage measurement is a more meaningful health indicator.

Research shows that people of Asian descent face higher health risks at lower BMI values. The WHO recommends: overweight at BMI 23+ and obese at BMI 27.5+, compared to 25 and 30 for the general population. Countries including Japan, China, Singapore, and India have adopted these adjusted cutoffs in clinical practice.

Waist-to-height ratio (WHtR) is calculated by dividing your waist circumference by your height. A healthy WHtR is generally below 0.5 (waist less than half your height). Some researchers argue WHtR is a better predictor of cardiovascular risk than BMI because it specifically measures abdominal fat. Combining BMI with WHtR gives a more complete picture of health risk.

In some countries, BMI is used as a screening tool that can influence life insurance or health insurance premiums. Applicants with a BMI above 30 or below 17.5 may face higher premiums or additional medical reviews. Additional health data (blood pressure, cholesterol, fitness level) can often provide important context for insurers.

A healthy weight range is derived from the BMI range of 18.5 to 24.9, applied to your height. The formula is: weight = BMI × height² (in metres). For example, at 170 cm, a healthy weight falls between approximately 53.5 kg and 72.0 kg. This calculator shows your personal healthy weight range automatically.

About This BMI Calculator

This free BMI Calculator uses the standard WHO formula to instantly classify your weight. It supports both metric (cm/kg) and imperial (ft–in/lbs) inputs. You get your BMI score, health category, and the healthy weight range for your height.

Healthy Weight by Height (Metric)

Height	Healthy Range (kg)
155 cm	44.5 – 59.9 kg
160 cm	47.4 – 63.7 kg
165 cm	50.3 – 67.7 kg
170 cm	53.5 – 72.0 kg
175 cm	56.7 – 76.3 kg
180 cm	60.0 – 80.7 kg
185 cm	63.3 – 85.2 kg

Healthy Weight by Height (Imperial)

Height	Healthy Range (lbs)
5'0"	97 – 130 lbs
5'3"	107 – 141 lbs
5'6"	118 – 154 lbs
5'9"	128 – 168 lbs
6'0"	140 – 183 lbs
6'3"	152 – 199 lbs

Standards & References

In-depth guides and technical articles.

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Health Jul 30, 2026

The Obesity Paradox: Why the BMI Mortality Curve Is U-Shaped

Some large studies find the lowest mortality in the "overweight" BMI band. The explanation is mostly confounding and reverse causation — here's how to read those findings.

Health Jun 30, 2026

Metabolic Syndrome Predicts Heart Disease Better Than BMI — Here's What the Five Criteria Are and Why They Matter More

Metabolic syndrome — any three of five criteria (waist circumference, triglycerides, HDL, blood pressure, fasting glucose) — predicts cardiovascular disease better than BMI alone, and "TOFI" individuals (normal BMI, high visceral fat) are misclassified as healthy by BMI. Here's the complete metabolic syndrome criteria, A Body Shape Index (ABSI) as the next-generation abdominal obesity measure, the obesity paradox in clinical populations, and why WHtR is emerging as the recommended companion to BMI.

Health Jun 21, 2026

How BMI Went From Population Statistics to Clinical Screening — And Why That History Matters

BMI was invented by statistician Adolphe Quetelet to study population distributions — and he explicitly said it was unsuitable for judging individuals. It took 150 years of insurance industry adoption, Ancel Keys' 1972 renaming, and a 1998 threshold change that reclassified 29 million Americans as "overweight" overnight for it to become a clinical screening tool. Here's the history of how a population statistic became a medical measure, and what that origin story explains about its limitations.

Health Jun 13, 2026

BMI and Pregnancy: Why Pre-Pregnancy BMI Matters and "Current BMI" During Pregnancy Doesn't Mean What You'd Think

A pregnant person's BMI increases throughout pregnancy simply because of the pregnancy itself — applying standard BMI categories to this changing number would be meaningless. Here's why clinical weight-gain guidance uses pre-pregnancy BMI as a fixed reference point instead, why "total weight gain from that reference point" is the relevant question rather than "current BMI category," and how postpartum BMI takes time to become meaningful again.

Health Jun 13, 2026

BMI and Ethnicity: Why the WHO Recommends Lower Thresholds for Asian Populations

A BMI of 24 is "normal" by standard categories but already represents "increased risk" under WHO's Asian-specific BMI cut-offs (23 for overweight, 27.5 for obese). Here's why these adjustments exist, the body composition research behind them, UK NICE guidance for multiple ethnic groups, and why waist circumference complements BMI across populations.