BMI Calculator
Enter your height and weight — in pounds and feet or kilograms and centimeters — to get your body mass index to one decimal place, your weight category on a color-coded gauge, and the healthy weight range for your height. Informational only, not medical advice.
Enter your weight and height to calculate your BMI.
How to Use BMI Calculator
Choose your units
Toggle between imperial (lbs, ft/in) and metric (kg, cm).
Enter height and weight
Type your measurements — the BMI updates instantly as you type.
Read your result
See your BMI, category on the color gauge, and the healthy weight range for your height.
About BMI Calculator
What BMI is and how it's calculated
Body mass index is your weight in kilograms divided by your height in meters squared (kg/m²); imperial inputs are converted first, equivalent to 703 × lbs ÷ in². The standard adult categories from the World Health Organization are: underweight below 18.5, normal weight 18.5–24.9, overweight 25–29.9, and obese 30 and above. Developed in the 1830s by Adolphe Quetelet as a population statistic, BMI persists because it's simple, free, and correlates reasonably well with body fat across large groups of people.
What BMI can't tell you
BMI measures mass, not composition — it cannot distinguish muscle from fat or say where fat is carried. Muscular athletes often register as 'overweight' while carrying very little fat; older adults can hold a 'normal' BMI while having lost muscle; and health risk varies with waist circumference, ethnicity, and fitness in ways BMI ignores (several health bodies use lower thresholds for people of Asian descent, for example). It also isn't valid for children and teens, who need age-and-sex-specific percentile charts, or during pregnancy.
Informational only — not medical advice
This calculator is for informational purposes only and is not a diagnosis; consult a healthcare provider for medical advice about your weight or health. A single number can't capture blood pressure, cholesterol, fitness, or body composition, and a 'normal' BMI doesn't guarantee good health any more than an 'overweight' one guarantees poor health. Everything computes locally in your browser — your height and weight are never uploaded or stored. Use the healthy-range output as a conversation starter with a professional, not a target imposed by a website.
Common uses for BMI Calculator
- Check which BMI category your current height and weight put you in
- Find the healthy weight range for your height before setting a fitness goal
- Convert and compare BMI using either metric or imperial measurements
- Track how your BMI shifts over months of training or a nutrition plan
- Prepare informed questions about weight for a doctor's appointment
Frequently Asked Questions
What formula does the BMI calculator use?
The standard formula: weight in kilograms divided by height in meters squared. If you enter pounds and feet/inches, they're converted to metric first (1 lb = 0.4536 kg, 1 in = 2.54 cm), which is mathematically identical to the imperial shortcut 703 × lbs ÷ in².
What are the BMI categories?
For adults, the WHO categories are: underweight below 18.5, normal weight 18.5–24.9, overweight 25–29.9, and obese 30 or above. The gauge marks these bands in color with your value on top. Some health authorities apply different cutoffs for certain populations, such as lower overweight thresholds for people of Asian descent.
Is BMI accurate for athletes or older adults?
Often not. BMI can't separate muscle from fat, so muscular people frequently score as overweight despite low body fat, and older adults who've lost muscle can score normal while carrying excess fat. Waist circumference, body-fat percentage, and a clinician's assessment give a fuller picture.
How is the healthy weight range calculated?
It's the weight span that would put your BMI between 18.5 and 24.9 at your entered height: multiply each threshold by your height in meters squared. For someone 5'8", that works out to roughly 122–164 lbs. It's a statistical range for adults, not a personal prescription.
Does BMI work for children?
Not with adult cutoffs. Children and teens (ages 2–19) are assessed using BMI-for-age percentile charts that account for sex and normal growth patterns — a pediatrician compares the child's BMI to peers of the same age and sex. This calculator is designed for adults only.