Calculate Your BMI Instantly
Body Mass Index is a quick screening measure of body weight relative to height. Enter your details below for an instant result, your BMI category, and a healthy weight range — based on WHO and CDC guidelines.
<18.5 Healthy
18.5–24.9 Over
25–29.9 Obese
30+
BMI is a screening tool, not a diagnosis. It doesn't measure body fat directly and may misclassify muscular or older adults. Talk to a healthcare provider about what your result means for you.
What is BMI?
Body Mass Index (BMI) estimates whether your weight is in a healthy range for your height. It's used worldwide by doctors and public health organizations as a fast, free screening measure for weight-related health risk.
A higher BMI is associated with increased risk of conditions like type 2 diabetes, high blood pressure, and heart disease — while a very low BMI can signal undernutrition. BMI doesn't distinguish muscle from fat, so it works best alongside other measures like waist circumference and body fat percentage.
Sources: WHO — A healthy lifestyle · CDC — About Adult BMI
BMI categories (WHO, adults)
How BMI is calculated
The same formula, in both unit systems:
BMI = weight (kg) ÷ height² (m²)
BMI = 703 × weight (lb) ÷ height² (in²)
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Frequently asked questions
What is a healthy BMI?
For most adults, a BMI between 18.5 and 24.9 is considered a healthy weight by the WHO and CDC. Below 18.5 is underweight, 25–29.9 is overweight, and 30 or above falls in the obesity range.
Is BMI accurate for everyone?
No. BMI is a screening tool, not a diagnostic one. It can overestimate body fat in muscular people (athletes, bodybuilders) and underestimate it in older adults who have lost muscle. Waist circumference and body fat percentage give a fuller picture.
Should I use metric or US units?
Either — the result is identical. Use the switch at the top of the calculator to enter feet/inches and pounds, or centimeters and kilograms.
How is BMI calculated?
BMI = weight in kilograms divided by height in meters squared. In US units: BMI = 703 × weight in pounds ÷ height in inches squared. For example, 70 kg at 1.75 m gives a BMI of 22.9.
Does BMI work for children and teens?
Children and teens (ages 2–19) use the same formula but a different interpretation: results are compared against CDC growth charts as an age- and sex-specific percentile. This calculator is designed for adults 20 and older.
How can I lower my BMI safely?
Sustainable changes work best: a modest calorie deficit (try our Calorie Calculator), more protein and whole foods, regular strength and cardio exercise, and adequate sleep. Aim for 0.5–1 lb per week and check with a doctor before major changes.
Is my data stored anywhere?
No. All calculations run in your browser — nothing you enter is sent to a server, saved, or shared.