BMI Calculator
Calculate your Body Mass Index to assess if your weight is healthy for your height.
Your Measurements
ft
in
lb
Your BMI Result
18.5
25
30
40
What is BMI?
Body Mass Index (BMI) is a simple calculation using your height and weight to estimate body fat. It’s widely used as a screening tool to identify potential weight problems in adults.
For example, a person who is 5’10” (178 cm) and weighs 170 lbs (77 kg) has a BMI of 24.3, which falls in the “Normal” range.
BMI Categories (WHO Standards)
The World Health Organization defines BMI categories for adults over 20 years old:
- Underweight (BMI < 18.5): May indicate malnutrition, eating disorders, or other health issues.
- Normal (BMI 18.5-24.9): Associated with lowest health risks for most people.
- Overweight (BMI 25-29.9): Increased risk of heart disease, diabetes, and hypertension.
- Obese (BMI ≥ 30): Significantly elevated health risks; may require medical intervention.
Tips for a Healthy BMI
- Balanced diet: Focus on whole foods, lean proteins, fruits, vegetables, and whole grains.
- Regular exercise: Aim for 150 minutes of moderate aerobic activity per week.
- Strength training: Building muscle mass can improve body composition even without weight change.
- Gradual changes: Losing 1-2 lbs per week is sustainable and healthier than crash diets.
BMI Limitations
- Doesn’t measure body fat directly: Athletes with high muscle mass may have “overweight” BMI despite low body fat.
- Age and sex differences: Women naturally have more body fat than men at the same BMI.
- Ethnic variations: Health risks may occur at different BMI thresholds for different populations.
- Not for children: Children and teens should use age-specific BMI percentiles instead.
Frequently Asked Questions
How is BMI calculated and what are the normal ranges?
BMI equals your weight in kilograms divided by your height in meters squared. The WHO categories are: Underweight below 18.5, Normal weight 18.5–24.9, Overweight 25–29.9, and Obese 30 or above. The calculator also shows your healthy weight range — the weight span that keeps your BMI between 18.5 and 24.9 for your specific height.
What is the ideal BMI for adults?
The WHO considers a BMI between 18.5 and 24.9 to be the normal or healthy range for most adults. The calculator also references a BMI of 22 as a common midpoint target. However, the optimal BMI for an individual depends on age, sex, ethnicity, and muscle mass. These are population-level guidelines, not absolute personal targets.
Why is BMI considered inaccurate for athletes and muscular people?
BMI uses total body weight relative to height and cannot distinguish between muscle and fat. A heavily muscled person may have a BMI in the overweight or obese range despite having low body fat. Conversely, someone with a normal BMI can have high body fat (called normal-weight obesity). For a more complete picture, combine BMI with a body fat percentage measurement.
Does BMI apply the same way for all ethnicities?
The standard WHO BMI cutoffs were developed primarily from data on European populations. Research suggests that people of Asian descent tend to carry more body fat at lower BMI values, and some health organizations recommend lower thresholds for Asian populations (overweight at 23, obese at 27.5). Consult a healthcare provider for interpretation specific to your background.
Can children use this BMI calculator?
This calculator uses adult WHO BMI categories and is designed for adults 18 and older. Children and teenagers require age- and sex-specific BMI-for-age percentile charts because healthy body composition changes during development. A healthcare provider should interpret BMI in children using pediatric growth references.