Enter your height and weight — in feet/pounds or centimeters/kilograms — to get your BMI, your weight category, and the healthy weight range for your height.
How BMI is calculated
Body Mass Index is a simple screening ratio of weight to height, used worldwide since the 1970s to flag potential weight-related health risk at a population level.
BMI = weight (kg) ÷ height² (m²) or BMI = 703 × weight (lbs) ÷ height² (in²)
BMI categories for adults
Below 18.5 — Underweight
18.5 – 24.9 — Healthy weight
25.0 – 29.9 — Overweight
30.0 and above — Obese
Worked example
Someone who is 5′10″ (70 inches) and weighs 165 lbs:
BMI = 703 × 165 ÷ 70² = 703 × 165 ÷ 4900 = 23.7 — inside the healthy range of 18.5–24.9, which for that height corresponds to roughly 129–174 lbs.
What BMI can and can't tell you
BMI is a useful first-pass screen, but it measures mass, not composition. A muscular athlete and a sedentary person can share the same BMI with very different health profiles. If your result is near a category boundary, or you're an athlete, older adult, or pregnant, the number deserves context from a healthcare provider. This calculator is for information only and isn't medical advice.
Frequently asked questions
What is a healthy BMI?
For most adults, a BMI between 18.5 and 24.9 is considered the healthy range. Below 18.5 is classed as underweight, 25 to 29.9 as overweight, and 30 or above as obese.
How is BMI calculated?
BMI is your weight in kilograms divided by your height in meters squared: BMI = kg ÷ m². In US units the formula is BMI = 703 × pounds ÷ inches².
What are BMI's limitations?
BMI doesn't distinguish muscle from fat, so muscular people can register as "overweight" while being lean, and it can underestimate body fat in older adults. It also doesn't account for where fat is carried. Treat it as a screening number, not a diagnosis — waist measurement and body composition tell a fuller story.
Does this BMI calculator work for children?
No — this calculator uses adult thresholds. For anyone aged 2–19, BMI must be interpreted against age-and-sex growth percentiles, which is a different calculation. Use a pediatric BMI percentile tool or ask your pediatrician.
Is BMI different for men and women?
The standard adult BMI formula and categories are the same for men and women. Women typically carry more body fat at the same BMI, which is one of the known limitations of using a single scale for everyone.