BMI Calculator
Calculate your Body Mass Index from your height and weight — in US units (ft/in, lbs) or metric — and see your BMI category against the standard ranges.
For general information only — not medical advice or a diagnosis. BMI is a screening tool that does not measure body fat directly and can misclassify very muscular or older people. Talk to your doctor about what a healthy weight is for you.
How BMI works
Body Mass Index compares your weight to your height: weight in kilograms divided by height in metres squared. In US units the same thing is BMI = 703 × weight(lbs) ÷ height(in)². It sorts adults into broad categories — under 18.5 underweight, 18.5–24.9 normal, 25–29.9 overweight, 30 and over obese — and is widely used as a quick population-level screen.
What BMI does and doesn’t tell you
BMI is a screening tool, not a diagnosis. Because it uses only height and weight, it can’t tell muscle from fat — a lean, muscular person may read “overweight,” and it can underestimate fat in older adults. Use it alongside a body fat estimate and your doctor’s advice. To plan around it, see your daily calories and TDEE.
Frequently asked questions
How do you calculate BMI?
BMI is your weight in kilograms divided by your height in metres squared (kg/m²). In US units the formula is BMI = 703 × weight(lbs) ÷ height(in)². For example, 160 lbs at 5′9″ (69 in) is 703 × 160 ÷ 69² ≈ 23.6. This calculator does the conversion for you.
What is a healthy BMI?
The standard adult ranges are: under 18.5 underweight, 18.5–24.9 normal weight, 25–29.9 overweight, and 30 or above obese. These are general screening categories, not a measure of health on their own.
Is BMI accurate for everyone?
BMI is a quick screen, not a diagnosis. It does not distinguish muscle from fat, so athletes can read “overweight” while having low body fat, and it can underestimate body fat in older adults. Use it alongside other measures and your doctor’s advice.
How is BMI different for men and women?
The BMI formula and adult categories are the same for men and women. Body composition differs on average, so for a fuller picture pair BMI with a body-fat estimate; this calculator focuses on the standard BMI value and category.