Separate tools for men and women
Switch tabs to get gender-specific guidance while using the same trusted BMI formula.
BMI Calculator
Calculate body mass index for men and women
Switch between the male and female tabs to calculate your BMI. Enter height and weight to instantly see your score, weight category, and healthy weight range.
How to calculate BMI
- 1
Choose male or female tab
Select the tab that matches you, then enter height and weight in metric or imperial units.
- 2
Click Calculate BMI
The calculator uses the standard formula: weight (kg) ÷ height (m)² — the same for men and women.
- 3
Review your results
See your BMI score, category, and the healthy weight range for your height.
Why use this BMI calculator
Healthy weight target
See the weight range linked to a BMI of 18.5–24.9 — a useful starting point for weight goals.
Free and private
No signup required. All calculations happen in your browser — your data stays on your device.
BMI Introduction
Body Mass Index (BMI) is a simple numerical measure of body fat based on height and weight. Developed in the 19th century by Adolphe Quetelet, it is widely used by healthcare providers as a quick screening tool to categorize weight status in adults and children.
BMI does not directly measure body fat, but correlates reasonably well with more direct measures in most people. It helps identify whether a person may be underweight, normal weight, overweight, or obese — categories linked to different health risk profiles.
Because BMI is easy to calculate and understand, it remains one of the most common tools in public health, clinical practice, and personal wellness tracking. However, it should always be interpreted alongside other health indicators.
BMI Table for Adults
For adults aged 20 and older, the World Health Organization (WHO) defines the following BMI categories. These fixed cutoffs apply equally to men and women.
| Category | BMI Range |
|---|---|
| Underweight | Below 18.5 |
| Normal weight | 18.5 – 24.9 |
| Overweight | 25.0 – 29.9 |
| Obese (Class I) | 30.0 – 34.9 |
| Obese (Class II) | 35.0 – 39.9 |
| Obese (Class III) | 40.0 or above |
BMI Table for Children and Teens, Age 2–20
For children and adolescents aged 2 to 20, BMI is interpreted using age- and sex-specific percentile charts from the CDC — not the adult cutoffs above. A child's BMI percentile compares their BMI to others of the same age and sex.
| Category | Percentile Range |
|---|---|
| Underweight | Less than 5th percentile |
| Healthy weight | 5th to less than 85th percentile |
| Overweight | 85th to less than 95th percentile |
| Obese | 95th percentile or above |
Percentile charts account for the fact that children grow at different rates. Always consult a pediatrician for interpretation.
BMI Chart for Children and Teens, Age 2–20
The chart below illustrates how BMI percentile curves change with age. Each colored band represents a weight category relative to peers of the same age and sex. An individual child's BMI is plotted against these curves to determine their percentile.
- Underweight
- Healthy weight
- Overweight
- Obese
This chart is for educational purposes. Official CDC growth charts should be used for clinical assessment.
Risks Associated with Being Overweight
Being overweight or obese (BMI ≥ 25 in adults) is associated with an increased risk of numerous health conditions. The higher the BMI, the greater the risk generally becomes.
- Type 2 diabetes and insulin resistance
- High blood pressure (hypertension) and cardiovascular disease
- Stroke and coronary heart disease
- Certain cancers (e.g., breast, colon, endometrial, kidney)
- Sleep apnea and breathing problems
- Osteoarthritis, fatty liver disease, and kidney disease
Risks Associated with Being Underweight
Being underweight (BMI below 18.5 in adults) can also pose health risks, especially when caused by malnutrition or underlying medical conditions.
- Nutrient deficiencies (vitamins, minerals, protein)
- Weakened immune system and increased infection risk
- Osteoporosis and increased fracture risk
- Fertility problems and pregnancy complications
- Anemia, fatigue, and muscle wasting
Limitations of BMI
While BMI is a useful screening tool, it has important limitations that should be considered when interpreting results:
- Does not distinguish between muscle and fat — athletes may have high BMI despite low body fat
- Does not account for fat distribution — abdominal fat carries higher risk than fat stored elsewhere
- May not be accurate for elderly adults who have lost muscle mass
- Different ethnic groups may have different health risks at the same BMI level
- Does not apply during pregnancy or for children without percentile charts
- Does not measure overall health, fitness, diet quality, or metabolic health
BMI Formula
BMI is calculated by dividing a person's weight in kilograms by the square of their height in meters. This formula is the same worldwide for all adults.
BMI = weight (kg) ÷ height (m)²
Example: 70 kg ÷ (1.75 m)² = 22.9
Using imperial units: multiply weight in pounds by 703, then divide by height in inches squared. Formula: BMI = 703 × weight (lbs) ÷ height (in)²
BMI Prime
BMI Prime is a simplified ratio that expresses your BMI relative to the upper limit of the normal range (BMI 25). It provides a quick sense of how far above or below the overweight threshold you are.
BMI Prime = BMI ÷ 25
A BMI Prime of 1.0 equals the upper limit of normal weight. Below 1.0 is normal; above 1.0 indicates overweight.
For example, a BMI of 22.5 gives a BMI Prime of 0.90 (10% below the overweight threshold), while a BMI of 30 gives a BMI Prime of 1.20 (20% above the threshold).
Ponderal Index
The Ponderal Index (PI) is an alternative body composition measure that cubes height instead of squaring it. It may be more reliable than BMI for very tall or very short individuals.
PI = weight (kg) ÷ height (m)³
Normal adult PI values typically range from 11 to 14 kg/m³. Values above 15 may indicate overweight.
Unlike BMI, the Ponderal Index is less sensitive to height extremes. It is sometimes used in pediatrics and neonatology, but BMI remains more common in general practice.
BMI calculator FAQ
Is the BMI formula different for men and women?+
No. BMI uses the same formula for everyone: weight in kilograms divided by height in meters squared. Men and women may interpret results differently because body composition varies.
What is a healthy BMI?+
For most adults, a BMI between 18.5 and 24.9 is considered normal weight. Below 18.5 is underweight, 25–29.9 is overweight, and 30 or above is obese.
Does muscle mass affect BMI?+
Yes. BMI does not distinguish between muscle and fat. Athletic men and women with higher muscle mass may have a higher BMI despite being healthy.
Which tab should I use?+
Choose the Male tab for men and the Female tab for women. The calculation is identical, but each tab shows guidance tailored to that gender.
What units does this calculator support?+
You can enter height and weight in metric (centimeters and kilograms) or imperial (feet/inches and pounds).
How accurate is a BMI calculator?+
BMI is a useful population-level screening tool but has limitations for individuals. Combine it with waist circumference, body composition, and professional medical advice.
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