BMI Calculator

Calculate your body mass index

US Units
Metric Units
Step 1: Basic Information
Step 2: Activity Level *(Optional)
Step 3: Select your goal *(Optional)
Your results:
Basal Metabolic Rate (BMR):
0
Body Mass Index (BMI):
0
Target calorie intake per day:
0
Macronutrient Balance:
Fats: 0 g
Protein: 0 g
Carbs: 0 g

Body Mass Index Chart

Use the BMI chart to determine your BMI rating. The table shows the World Health Organization BMI classification system. The rating scale is the same for males and females.

Body Mass IndexStatus
Below 18.5Underweight
18.5–24.9Normal weight
25.0–29.9Pre-obesity
30.0–34.9Obesity class I
35.0–39.9Obesity class II
Above 40Obesity class III

What is Body Mass Index (BMI)?

The body mass index (BMI) is a weight-for-height ratio computed by dividing the weight in kilograms by the square of the height in meters (kg/m2). Although the BMI is frequently used as a proxy for body fatness, it is actually a surrogate for body fat because it measures extra weight rather than excess fat. Despite this, research has established a correlation between BMI and other direct measures of body fat, such as underwater weighing and dual energy x-ray absorptiometry.

Why is BMI used?

BMI is a straightforward, low-cost, and noninvasive proxy for body fat. In comparison to other approaches, BMI is based purely on height and weight, and anyone with access to the appropriate equipment can have their BMI tested and calculated on a routine basis with reasonable accuracy.
Additionally, studies have demonstrated a correlation between BMI and body fat and future health concerns. A high BMI is associated with an increased risk of illness and mortality in the future. As a result, BMI is an appropriate screening tool for obesity and its associated health hazards.
Finally, the widespread and long-standing use of BMI contributes to its population-level utility. Its use has resulted in an increase in the availability of published population data, enabling public health professionals to draw comparisons across time, geographies, and subsets of the population.

What are some points to consider when calculating an adult's BMI?

Consider the clinical constraints of BMI. Because BMI is a measure of extra weight rather than excess body fat, it serves as a substitute for body fatness.

Age, gender, ethnic origin, and muscle mass all have an effect on the link between BMI and body fat. Additionally, BMI makes no distinction between excess fat, muscle, or bone mass, and gives no indication of how fat is distributed among individuals.

The following are a few instances of how specific variables can affect how BMI is interpreted:

  • On average, older persons have more body fat than younger ones with a similar BMI.
  • On average, women have more total body fat than men with a comparable BMI.

What are some points to consider when calculating a child's or adolescent's BMI?

The difficulties against using BMI as a measure of adulthood also apply to children and adolescents. Other variables, such as height also affect the link between BMI and body fat in children.

Additionally, the accuracy of BMI varies significantly depending to the degree of body fatness in each child. BMI is a good indicator of extra body fat in obese children (or those with a BMI-for-age more than or equal to the 95th percentile). However, in overweight children (or those with a BMI between the 85th and 94th percentiles for their age), elevated BMI levels can be the result of increased fat or fat-free mass. Similarly, disparities in BMI among relatively thin children are frequently explained by variances in fat-free mass.

What other body fat measurements are available?

Other measures of body fat, such as skinfold thicknesses, bioelectrical impedance, underwater weighing, and dual energy x-ray absorption, may be more accurate than BMI, according to some study. The waist circumference (sometimes divided by height) is another easy way to assess fat distribution. Although these assessments may provide a more accurate assessment of an individual’s body fatness and risk of obesity-related health problems, they can be costly, intrusive, not widely available, or difficult to standardize between observers or machines. Because they are technically hard and rely on more advanced technologies, several of these metrics are deemed unsuitable for ordinary clinical practice.


Furthermore, the majority of our understanding of obesity-related health hazards is based on the relationship of BMI to other outcomes. There are few reference standards for body fatness based on the above-mentioned metrics, and without established risk categories, determining whether an individual’s body fatness is low, moderate, or high is challenging. As a result, additional body fat measurements are not suggested for frequent use.

What should we draw from BMI?

For both adults and children, BMI Calculator is a reliable indication of body fat. BMI should not be utilized as a diagnostic tool because it does not directly assess body fat. Instead, BMI should be used to assess population weight status and as a screening tool to identify prospective weight concerns in individuals.