BMI Calculator

The Body Mass Index (BMI) calculator provides an estimate of your body fat based on your height and weight. BMI is a widely used screening tool that helps identify potential weight problems in adults and categorizes your weight status as underweight, normal, overweight, or obese.

While BMI doesn't directly measure body fat, it offers a simple and inexpensive method to assess weight categories that may lead to health problems. Enter your height and weight to calculate your BMI and see where you fall on the BMI scale.

Unit System

Metric (kg, cm)

Imperial (lb, in)

Weight (kg)

Height (cm)

Learn More About BMI

Body Mass Index (BMI) is a numerical value derived from a person's weight and height. It provides a simple way to classify individuals as underweight, normal weight, overweight, or obese.

The BMI formula is calculated as follows:

Metric: BMI = weight(kg) / height²(m²)

Imperial: BMI = 703 × weight(lb) / height²(in²)

For example, if you weigh 70 kg and are 1.75 meters tall, your BMI would be:

BMI = 70 / (1.75 × 1.75) = 70 / 3.0625 = 22.9

The BMI was developed by Belgian mathematician Adolphe Quetelet in the 1830s as a simple way to assess the degree of obesity in populations, making it easier to study the growing rates of obesity.

BMI results are typically categorized as follows:

Underweight: BMI less than 18.5

Being underweight can indicate malnutrition, an eating disorder, or other health problems. It may weaken your immune system, increase risk of infections, cause bone loss, and lead to fertility issues.

Normal weight: BMI 18.5 to 24.9

This range is associated with the lowest risk for health problems. Maintaining a healthy weight can reduce your risk of heart disease, stroke, diabetes, and high blood pressure.

Overweight: BMI 25 to 29.9

Being overweight increases your risk of heart disease, stroke, type 2 diabetes, high blood pressure, and certain cancers. Even modest weight loss can improve or prevent health problems associated with being overweight.

Obese: BMI 30 or higher

Obesity significantly increases the risk of developing serious health problems, including heart disease, stroke, diabetes, certain types of cancer, sleep apnea, and osteoarthritis. The higher your BMI, the greater your risk.

It's important to note that these categories are based on BMI values for adults aged 20 and over, regardless of gender. Different BMI ranges apply to children and teenagers.

While BMI is a useful screening tool, it has several limitations and should not be used as the sole diagnostic tool for determining health status:

Doesn't account for body composition: BMI doesn't distinguish between muscle and fat. Athletes with high muscle mass may have a high BMI but low body fat.
Ignores differences in body types: It doesn't account for variations in body proportions or distribution of fat, which can be significant health indicators.
Age considerations: As people age and lose muscle mass, their BMI may remain the same even though they have more body fat.
Ethnic and racial variations: Different ethnic groups may have different body compositions and health risks at the same BMI values.
Doesn't consider other health factors: Blood pressure, cholesterol levels, blood sugar, family history, and lifestyle habits are important health indicators not captured by BMI.

For a more comprehensive health assessment, BMI should be used alongside other measurements like waist circumference, body fat percentage, and specific health screenings.

If your BMI falls outside the "normal" range (18.5-24.9), here are some evidence-based strategies that may help you achieve a healthier weight:

For those with a BMI below 18.5:

Increase calorie intake with nutrient-dense foods
Add healthy fats like avocados, nuts, and olive oil to your diet
Eat smaller meals more frequently throughout the day
Incorporate strength training to build muscle mass
Consult with a healthcare provider to rule out underlying medical conditions

For those with a BMI above 25:

Focus on a balanced diet rich in fruits, vegetables, lean proteins, and whole grains
Practice portion control and mindful eating
Gradually increase physical activity, aiming for at least 150 minutes of moderate exercise per week
Reduce consumption of processed foods, sugary drinks, and high-calorie snacks
Establish healthy sleep patterns and stress management techniques
Consider working with healthcare professionals for personalized guidance

Remember that sustainable weight management is about making long-term lifestyle changes rather than following short-term, extreme diets. Small, consistent changes often lead to the most lasting results.

Always consult with healthcare professionals before making significant changes to your diet or exercise routine, especially if you have existing health conditions or concerns.

While BMI is widely used, several alternative measurements can provide additional insights into health status:

Waist Circumference

Measures abdominal fat, which is a better predictor of obesity-related health risks. A waist circumference of more than 40 inches (102 cm) for men and 35 inches (88 cm) for women indicates increased health risks.

Waist-to-Hip Ratio (WHR)

Compares waist circumference to hip circumference. A ratio above 0.9 for men and 0.85 for women suggests excess abdominal fat and increased health risks.

Body Fat Percentage

Directly measures the proportion of fat in your body. Methods include skinfold measurements, bioelectrical impedance, DEXA scans, and underwater weighing. Healthy ranges vary by age and gender.

Body Adiposity Index (BAI)

Estimates body fat percentage using hip circumference and height. It was developed as an alternative to BMI that doesn't require weight measurement.

Relative Fat Mass (RFM)

A newer index that uses height and waist circumference to estimate body fat percentage. Some research suggests it may be more accurate than BMI for this purpose.

For a comprehensive assessment of health and fitness, it's beneficial to use multiple measurements and consult with healthcare professionals who can interpret results in the context of your overall health.

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Frequently Asked Questions

How is BMI calculated?

BMI is your weight in kilograms divided by your height in meters squared: BMI = kg / m². In imperial units, the formula is BMI = 703 × pounds / inches². For example, someone who is 5'10" (70 inches) and 175 lbs has a BMI of 703 × 175 / 70² ≈ 25.1.

What is a healthy BMI range?

For most adults, a BMI between 18.5 and 24.9 is considered a healthy weight. Below 18.5 is classified as underweight, 25 to 29.9 as overweight, and 30 or above as obese. These ranges are guidelines for the general population, not a diagnosis.

Is BMI accurate for athletes and muscular people?

BMI does not distinguish between muscle and fat, so muscular people often score in the overweight range despite low body fat. If you carry a lot of muscle, measures such as waist circumference, waist-to-height ratio, or body fat percentage give a more accurate picture.

Is the BMI formula different for men and women?

No — the BMI formula and the standard weight categories are the same for adult men and women. For children and teens aged 2–19, BMI is interpreted using age- and sex-specific percentile charts instead of fixed cutoffs.