BMI Calculator – Calculate Body Mass Index from Height and Weight
Estimate your body mass index (BMI) using gender, age, height, and weight in metric or imperial units. Enter your details, click Calculate BMI, and see your BMI value. Ages 20+ also see the matching WHO adult category (underweight, normal, overweight, or obese). This tool is free and intended for general informational use.
Results are for general information only and are not a medical diagnosis. Gender and age are required for context. Adult WHO categories apply from age 20; younger ages need age- and sex-specific charts. When you calculate, age, gender, height, weight, BMI, and IP address may be stored for product analytics. Consult a healthcare professional for personalized advice.
Disclaimer
This BMI Calculator is provided for general information and educational purposes only. Body mass index is a screening estimate based on height and weight. It does not diagnose body fatness, malnutrition, or any medical condition, and it does not replace advice from a doctor, dietitian, or other qualified healthcare professional.
Web4pps does not provide medical advice. Always speak with a healthcare professional before making decisions about diet, exercise, weight management, or treatment. BMI may be less useful for athletes, pregnant people, children, older adults, and anyone with conditions that affect muscle mass or body composition.
How to Use BMI Calculator
Follow these steps to estimate body mass index with this free online tool:
- Choose a unit system — select Metric (kg and cm) or Imperial (lb, ft, and in).
- Select your gender — Female or Male (required).
- Enter your age — whole years from 2 to 120 (required). Ages 20+ use WHO adult categories; ages 2–19 show BMI with a pediatric chart caveat.
- Enter your height — in centimeters for metric, or feet and inches for imperial.
- Enter your weight — in kilograms or pounds, matching the unit system you selected.
- Click Calculate BMI — your BMI value appears with age and gender. Adults also see the matching WHO category and a quick category reference table. If the adult result is underweight, overweight, or obese, a suggested weight range to reach a Normal BMI at your height is shown below the table.
The calculator uses the standard formula BMI = weight (kg) ÷ height (m)². Imperial inputs are converted to metric before the result is computed. Gender does not change the adult WHO cutoffs; age determines whether adult categories are shown.
Who should use BMI Calculator
This tool is best suited for adults (age 20+) who want a quick, general estimate of how their weight relates to height using World Health Organization (WHO) adult BMI categories. Younger users can still compute BMI, but should rely on age- and sex-specific growth charts with a clinician for interpretation.
- Adults tracking general weight category for personal awareness or wellness goals.
- People comparing height and weight trends over time as one of several health markers.
- Anyone who needs a simple free BMI estimate in metric or imperial units without creating an account.
BMI has limits. It may overestimate body fat in muscular athletes and underestimate risk in older adults with lower muscle mass. It is not designed as a substitute for pediatric growth charts, and it is not appropriate for assessing pregnancy. Use clinical judgment and professional guidance alongside any BMI result.
Frequently Asked Questions
What is BMI?
Body mass index (BMI) is a number calculated from height and weight. It is commonly used as a simple screening tool to classify adults into underweight, normal weight, overweight, or obese ranges.
How is BMI calculated?
In metric units, BMI equals weight in kilograms divided by height in meters squared. For imperial inputs, this calculator converts pounds and feet/inches into kilograms and meters first, then applies the same formula.
Why do you ask for gender and age?
Gender and age are required for context. WHO adult BMI ranges are the same for females and males and apply from age 20. For ages 2–19, BMI should be interpreted with age- and sex-specific growth charts rather than adult cutoffs.
What are the WHO adult BMI categories?
Underweight is below 18.5, normal is 18.5–24.9, overweight is 25–29.9, and obese is 30 or above. These ranges apply to adults (age 20+) and may not fit every individual.
Can I use metric and imperial units?
Yes. Switch between Metric (kg, cm) and Imperial (lb, ft/in) before you calculate.
Is BMI an accurate measure of health?
BMI is only one indicator. It does not measure body fat directly and does not fully account for muscle mass, bone density, ethnicity, or medical history. A healthcare professional can interpret BMI in context with other assessments.
Is this BMI calculator free?
Yes. You can use it as often as you like at no cost.
Is my height and weight stored?
When you click Calculate BMI, we may store age, gender, height, weight, BMI, and IP address for product and analytics purposes. See Privacy Information below.
Privacy Information
BMI is calculated in your browser. When you use Calculate BMI, Web4pps may save age, gender, height (cm and ft/in), weight (kg and lb), BMI, and IP address in our database for product and analytics use. You can use the tool without creating an account. Do not enter information you are uncomfortable sharing for this purpose.
