BMI Calculator
Your BMI in US or metric units — plus an honest explanation of what the number does and doesn’t mean.
Calculate your body mass index
How BMI is calculated
Body mass index is your weight divided by the square of your height, in metric units:
Example: someone 5’10″ (70 inches) weighing 175 pounds has a BMI of 703 × 175 ÷ 70² = 25.1. Standard adult categories: under 18.5 underweight, 18.5–24.9 healthy weight, 25–29.9 overweight, 30+ obesity.
What BMI is actually for
BMI was designed as a quick screening tool for populations. It correlates with body fat across large groups and costs nothing to calculate. Public-health researchers and doctors use it as a first-pass flag — a reason to look closer, not a verdict.
What BMI can’t tell you
BMI cannot distinguish muscle from fat, doesn’t know where you carry weight, and ignores age, sex, and frame. A muscular athlete can score “oveweight” while carrying very little body fat. Waist circumference, body-fat percentage, blood pressure, and lab work all say more about health than BMI alone.
Waist circumference matters more than BMI
Visceral fat around your organs is metabolically active. A waist above 35 inches for women and 40 inches for men adds cardiovascular risk at any BMI level. A simple rule: keep your waist below half your height (waist-to-height ratio under 0.5).
BMI and ethnicity
People of Asian descent carry more metabolic risk at lower BMI values. Several countries use lower thresholds (23 for overweight, 27.5 for obese) for Asian populations. Standard US cutoffs underestimate risk for this group.
Is BMI accurate for athletes?
Often not. Muscle is denser than fat, so muscular people frequently score “oveweight” or higher while being lean. Body-fat percentage is far more informative for athletes.
Does this calculator work for children?
No — these are adult categories. Children and teens use BMI-for-age percentiles that account for growth. A pediatrician can interpret those properly.
What’s a healthy weight for my height?
The calculator shows the weight range for a BMI of 18.5–24.9 at your height. Research shows lowest mortality risk in the 22–25 range for most adults, with older adults doing well at 25–27.
Should I worry about a BMI of 25–27?
Context matters. BMI slightly over 25 with good waist measurement, blood pressure, and labs is very different from the same number with poor markers. Discuss the full picture with a doctor.
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