BMI Calculator

Enter your height and weight above to find out your BMI in seconds. Body mass index is a calculated measure of weight relative to height. It gives you a quick screening number, not a diagnosis.

BMI is used by healthcare providers, the CDC, and the World Health Organization as a starting point for weight status conversations. It works well as a general estimate of body fat for most people, but it is not a perfect measure on its own.

This calculator is an estimate. It is not intended to diagnose disease or illness, and it is not a substitute for professional medical advice. Talk with a health care provider about what your results mean for your overall health.

Adult BMI Calculator

This adult BMI calculator is designed for men and women ages 20 and older. Enter your height and weight, and the tool returns your BMI value along with the standard weight status category.

For children and adolescents ages 2 through 19, BMI is calculated differently. It uses age and sex percentiles instead of fixed cutoffs. See the section below on the CDC BMI calculator for children and teens.

How to Calculate Your BMI

Body Mass Index Formula

The body mass index formula divides your weight by the square of your height.

Metric: BMI = weight (kg) ÷ height (m)²

Imperial: BMI = [weight (lb) ÷ height (in)²] × 703

For example, a person who weighs 70 kg and stands 1.75 m tall would calculate BMI as 70 ÷ (1.75 × 1.75) = 22.9.

Using the calculator here handles the math for you. Just enter your height and weight in either unit system.

Height and Weight Measurement

Accurate input gives you a more useful result. A few tips:

• Measure height without shoes, standing straight against a wall
• Weigh yourself in the morning before eating, wearing light clothing
• Use the same scale each time to track changes consistently

Even small measurement errors can shift your BMI by a point or more, so consistency matters.

What Your Body Mass Index Means

BMI results fall into standard categories established by the World Health Organization and the CDC. These ranges apply to adult men and women.

Underweight, Healthy Weight, Overweight, and Obese Ranges

A BMI of 25 or higher is generally classified as overweight. A BMI of 30 or above falls into the obese category.

These are screening categories, not final judgments. Whether a person is underweight, at a healthy weight, overweight, or obese depends on more than a single number. Your healthcare provider considers physical exam findings, lab work, and your full health history.

Is a 23 BMI chubby? No. A BMI of 23 falls squarely in the normal weight range. It does not indicate excess body fat by standard screening criteria.

Is 140 lbs overweight for 5ft, 4in tall? That gives a BMI of about 24.0, which is within the healthy weight range. It is close to the upper end, but it is not classified as overweight.

Body Fat, Muscle Mass, and Body Composition

BMI is a screening measure, not a direct measurement of body fat. It does not distinguish between fat, muscle, bone, or other tissue mass.

This matters for certain groups:

• Athletes and muscular individuals may have a high BMI because of their muscle mass, not excess fat
• Older adults may carry more body fat at the same BMI than younger adults
• Body composition (the ratio of fat to lean tissue) gives a more complete picture than BMI alone

Tools like skinfold measurements, DEXA scans, or bioelectrical impedance provide more direct estimates of body fat. BMI is not a perfect stand-in for these, but it is free, fast, and useful as a first step.

BMI Calculator and Health Risk

A high BMI is associated with an increased risk of several serious health conditions. It is one factor among many that your healthcare provider may evaluate.

Obesity, Type 2 Diabetes, and High Blood Pressure

Research consistently links obesity (BMI of 30 or higher) to higher rates of:

• Type 2 diabetes. Excess body fat affects how your body uses insulin.
• High blood pressure. A larger body requires more blood flow, which increases pressure on artery walls.
• Sleep apnea and joint problems. Extra weight strains joints and can narrow airways during sleep.

Overweight BMI values (25 to 29.9) also carry elevated risk, though generally less than the obese range.

Cholesterol and Cardiovascular Disease

Higher BMI correlates with unfavorable cholesterol levels, including higher LDL ("bad" cholesterol) and lower HDL ("good" cholesterol). Over time, this pattern raises the risk of cardiovascular disease, including heart attack and stroke.

BMI alone does not predict heart disease. A healthcare provider will consider cholesterol numbers, blood pressure, family history, smoking status, and other factors alongside your BMI to assess your overall health and potential health risks.

CDC BMI Calculator for Children and Adolescents

BMI for children and teens ages 2 through 19 years works differently than for adults. A child's body fat changes with age and differs between boys and girls, so a raw BMI number does not map to the same adult categories.

Growth Charts and Percentiles

The CDC BMI percentile calculator for children and teens compares a child's BMI to others of the same sex and age using growth charts. The result is a percentile ranking.

A child BMI at the 60th percentile means the child has a higher BMI than 60% of children of the same age and sex. This is well within the healthy range.

These growth charts were developed by the Centers for Disease Control and Prevention. If you need a child or teen BMI assessment, the CDC provides a dedicated calculator that factors in sex and age automatically.

What is a good BMI for my age? For adults, the healthy range (18.5 to 24.9) does not change with age. For children and teens, "good" depends on the age-and-sex percentile, not a fixed number.

Maintaining a Healthy Weight With Physical Activity

BMI gives you a snapshot. Maintaining a healthy body weight over time is what matters most for overall health and well-being.

Physical activity plays a central role. General guidelines recommend:

• At least 150 minutes of moderate aerobic activity per week (brisk walking, cycling, swimming)
• Muscle-strengthening activities at least two days per week
• Reducing extended sedentary time throughout the day

You do not need a gym membership. Walking, gardening, and bodyweight exercises all count. Even modest increases in physical activity can improve cholesterol, blood pressure, and blood sugar levels.

Pair regular movement with balanced eating habits. Small, sustainable changes tend to work better than drastic diets. A healthcare provider or registered dietitian can help you build a plan based on your BMI results, health history, and personal goals.

What This BMI Calculator Does Not Tell You

BMI is a useful screening tool, but it has clear limits. Here is what it cannot do:

• Measure body fat directly. It estimates body fat based on height and weight, but does not account for body composition.
• Distinguish fat from muscle. BMI is not accurate for people with high muscle mass, such as athletes or heavy laborers.
• Account for fat distribution. Where you carry fat (belly vs. hips) affects health risk. BMI does not capture this. Waist circumference is a better indicator.
• Replace a medical evaluation. BMI is not a diagnostic tool. It does not factor in age, sex, ethnicity, bone density, or fitness level.
• Apply directly to children. Adult BMI categories do not work for children and adolescents. Use age-and-sex percentile charts instead.

Use this BMI calculator as a quick, free starting point. Then bring your results to a healthcare provider who can interpret them alongside a full picture of your health, including physical exam findings, blood work, and your personal history.