BMI Calculator
Calculate your body mass index from your height and weight, and see which WHO category it falls in.
Result
Enter height and weight to see the result.
https://calcgallery.com/body-composition/bmi-calculator/
How to use the BMI Calculator
- Enter your height. The calculator accepts feet and inches or centimetres.
- Enter your weight in pounds or kilograms.
- Read your BMI and which WHO category it falls in.
- Check the healthy weight range shown for your height.
How it is calculated
Body mass index divides your weight in kilograms by the square of your height in metres:
BMI = weight (kg) ÷ height (m)²Whatever units you type in, the calculator converts to SI before dividing, so entering your height in feet and inches and your weight in pounds gives the same result as entering centimetres and kilograms.
What BMI does not tell you
BMI cannot distinguish muscle from fat. It does not account for where fat sits on your body, which matters for metabolic health. And the classification bands were derived primarily from studies of European adult populations, so they do not capture the full picture for every ethnicity and body type. A muscular athlete and a sedentary person of the same height and weight receive the same number.
Because of these limitations, BMI is not valid for children, teenagers under 18, pregnant people, or anyone with unusually high muscle mass. For children and adolescents, clinicians use BMI-for-age percentile charts from the CDC or WHO, which compare a young person’s BMI against others of the same age and sex rather than applying a single fixed threshold.
The World Health Organization classifies adult BMI into these bands:
| BMI range | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 to 24.9 | Normal weight |
| 25.0 to 29.9 | Overweight |
| 30.0 to 34.9 | Obese class I |
| 35.0 to 39.9 | Obese class II |
| 40.0 and above | Obese class III |
The calculator also shows a healthy weight range for your height, computed as the mass that would give a BMI between 18.5 and 24.9.
Practical tips
BMI does not measure body fat directly. It is a ratio of weight to height, nothing more. Two people with the same BMI can have very different amounts of body fat, and body fat is what matters for most health outcomes.
Athletes and muscular people commonly score overweight or obese. The extra weight comes from muscle, not fat, so the number does not carry the health implications usually associated with those categories. If you train regularly and carry significant muscle mass, BMI on its own says little about your health.
Waist circumference is a useful companion measurement. Where fat sits on the body matters as much as how much there is. Abdominal fat is more strongly associated with cardiovascular and metabolic risk than fat stored on the hips or thighs. A simple tape measure around the waist adds context that BMI cannot provide.
The formula was designed for populations, not individuals. Adolphe Quetelet developed the index in the 1830s to characterise the average build of entire populations. Applying population-level statistics to a single person ignores individual physiology, frame size and muscle mass.
Consult a healthcare professional rather than acting on a number alone. A BMI value is, at best, a reason to start a conversation with a clinician who can consider your full medical history, blood work and lifestyle before drawing any conclusions.
With your numbers
- 5 ft 10 in is 1.78 m, and 180 lb is 81.6 kg
- Healthy weight at 1.78 m: 128.9 lb to 173.5 lb
- BMI = 81.6 kg ÷ (1.78 m)² = 25.8, which is overweight
Quick reference
BMI is a screening estimate, not a clinical measurement of body fat.
| Example | BMI |
|---|---|
| 5 ft 4 in, 130 lb | 22.3 |
| 5 ft 6 in, 150 lb | 24.2 |
| 5 ft 10 in, 180 lb | 25.8 |
| 6 ft 0 in, 200 lb | 27.1 |
| 160 cm, 55 kg | 21.5 |
| 170 cm, 70 kg | 24.2 |
| 175 cm, 80 kg | 26.1 |
| 180 cm, 90 kg | 27.8 |
Where the numbers come from
The fixed figures this calculator relies on, and the published source each one was checked against. How the calculators are built and checked
3 sources
WHO Technical Report Series 894 (2000), Obesity: preventing and managing the global epidemic, Table 2.1, p. 9, https://iris.who.int/handle/10665/42330: underweight <18.50, normal range 18.50-24.99, preobese 25.00-29.99, obese class I 30.00-34.99, class II 35.00-39.99, class III ≥40.00.
Used for
- Upper boundary of the WHO underweight band.
- Lower boundary of WHO obesity class II.
- Lower boundary of WHO obesity class III.
WHO Technical Report Series 894 (2000), Obesity: preventing and managing the global epidemic, Table 2.1, p. 9, https://iris.who.int/handle/10665/42330: underweight <18.50, normal range 18.50-24.99, preobese 25.00-29.99, obese class I 30.00-34.99, class II 35.00-39.99, class III ≥40.00. The one-decimal edge is the one IOM/NRC, Weight Gain During Pregnancy (2009), Table S-1, p. 2, prints ("18.5-24.9 kg/m²"); health-shared.ts classifies below the next band's lower edge (25.0, 30.0), so both tables give the same band.
Used for
- Upper boundary of the WHO normal BMI band.
WHO Technical Report Series 894 (2000), Obesity: preventing and managing the global epidemic, Table 2.1, p. 9, https://iris.who.int/handle/10665/42330: underweight <18.50, normal range 18.50-24.99, preobese 25.00-29.99, obese class I 30.00-34.99, class II 35.00-39.99, class III ≥40.00. The one-decimal edge is the one IOM/NRC, Weight Gain During Pregnancy (2009), Table S-1, p. 2, prints ("25.0-29.9 kg/m²"); health-shared.ts classifies below the next band's lower edge (25.0, 30.0), so both tables give the same band.
Used for
- Upper boundary of the WHO overweight BMI band.
Common questions about the BMI Calculator
- Is BMI accurate?
- BMI is a screening tool, not a diagnostic one. It correlates with body fat at a population level but cannot distinguish muscle from fat or tell you where fat sits. A trained athlete and a sedentary person of the same height and weight get identical numbers. Treat it as a starting point, not a verdict.
- What is a healthy BMI?
- The WHO defines 18.5 to 24.9 as normal weight. Below 18.5 is underweight, 25.0 to 29.9 is overweight, and 30 or above is obese. These thresholds were set from large epidemiological studies linking BMI ranges to health outcomes across populations.
- Does BMI differ by sex or ethnicity?
- The standard WHO thresholds do not vary by sex. They do vary by population: the WHO notes that some Asian populations face elevated health risks at lower BMI values, with suggested action points of 23 for overweight and 27.5 for obese, rather than 25 and 30. This calculator uses the international thresholds; if you are in an affected population, discuss the lower cut-offs with your clinician.
- What should I do about my BMI result?
- Talk to a clinician. A number on a screen cannot account for your medical history, body composition, fitness level or overall health. A doctor or registered dietitian can interpret it alongside waist circumference, blood work and your own context.
- Is BMI valid for children?
- No. Children and teenagers grow at different rates, so a fixed threshold does not apply. Paediatric practice uses BMI-for-age percentile charts from the CDC or WHO, which compare a child against others of the same age and sex. This calculator is designed for adults aged 18 and over.