BMI Calculator
Calculate your body mass index in metric or imperial units, and see where it falls on the standard scale.
BMI Calculator
Your BMI
22.7
Healthy range
125.3 lb
to 168.6 lb
Category
Healthy weight
Status
In range
Height
175 cm
69.0 in
The standard BMI categories
- UnderweightUnder 18.5
- Healthy weight18.5 - 24.9
- Overweight25 - 29.9
- Obesity30 and above
BMI cannot tell muscle from fat. A muscular build can read as overweight while carrying very little body fat, and a low-muscle build can read as healthy while carrying too much. Treat this as one screening figure among several.
How the bmi calculation works
Body mass index is a single number relating your weight to your height. It was designed in the 1830s by Adolphe Quetelet as a way to describe populations, and it became a clinical screening tool because it is cheap, fast, and needs nothing but a scale and a tape measure.
The formula is:
BMI = weight (kg) ÷ height (m)²
In imperial units the same relationship is written BMI = 703 × weight (lb) ÷ height (in)², where 703 is just the unit conversion.
A worked example: someone 70 kg and 175 cm tall. Height in meters is 1.75, squared is 3.0625. So BMI = 70 ÷ 3.0625 = 22.9, which sits in the middle of the healthy range.
The World Health Organization categories for adults are:
- Under 18.5 — underweight
- 18.5 to 24.9 — healthy weight
- 25.0 to 29.9 — overweight
- 30.0 and above — obesity
For that 175 cm height, the healthy band works out to 56.7 kg to 76.3 kg — a 20 kg spread, which is worth remembering when a single number feels precise.
Where BMI genuinely misleads. Because it uses total weight, BMI cannot distinguish muscle from fat. A muscular athlete frequently lands in the "overweight" or even "obese" range while carrying very little body fat. The reverse also happens: someone with low muscle mass can sit at a healthy BMI while carrying an unhealthy amount of fat, a pattern sometimes described as normal-weight obesity.
It is also less reliable at the extremes of height, because the squared term does not scale perfectly, and it was derived from predominantly European populations — several health bodies use a lower overweight threshold of 23 for people of South Asian descent, where cardiometabolic risk rises at a lower BMI.
BMI is a screening indicator, not a diagnosis. Waist circumference, waist-to-height ratio, body fat percentage, blood pressure, and blood glucose all describe health more directly. Treat this number as one input among several, and talk to a doctor before drawing conclusions from it.
Disclaimer: This calculator provides estimates for general information only and is not medical advice. It cannot account for your medical history, body composition, or individual needs. Talk to a doctor or registered dietitian before making changes to your diet or exercise.
Frequently asked questions
What is a healthy BMI?
For adults, the World Health Organization defines 18.5 to 24.9 as the healthy weight range. Below 18.5 is classed as underweight, 25 to 29.9 as overweight, and 30 or above as obesity. These thresholds apply to adults only - children and teenagers are assessed against age and sex percentile charts instead.
Is BMI accurate for athletes?
Often not. BMI uses total body weight and cannot separate muscle from fat, so muscular people frequently register as overweight or obese despite low body fat. If you carry significant muscle, body fat percentage or waist measurement will describe your health far better.
How do I calculate BMI by hand?
In metric, divide your weight in kilograms by your height in meters squared. In imperial, multiply your weight in pounds by 703, then divide by your height in inches squared. For example, 154 lb and 69 in gives 703 x 154 / 4761 = 22.7.
Does BMI differ for men and women?
The thresholds are the same for adult men and women. Women naturally carry a higher proportion of body fat at the same BMI, so identical numbers can mean different body compositions - another reason to treat BMI as a screening figure rather than a complete picture.
What should I use instead of BMI?
Waist circumference and waist-to-height ratio are better indicators of the abdominal fat linked to metabolic risk. Keeping your waist under half your height is a widely used guideline. Body fat percentage, blood pressure, and blood glucose give a fuller picture than any weight-based measure alone.