BMI Calculator
Check Your Body Mass Index Instantly
The BMI Calculator helps you find out if your weight is healthy for your height and age. Simply enter your age, height, and weight, then click Calculate to see your BMI result.
BMI introduction
BMI (Body Mass Index) is a number that estimates body fat based on your height and weight. It classifies results into Underweight, Normal, Overweight, and Obese categories.
BMI table for adults
| Classification | BMI range (kg/m²) |
|---|---|
| Severe Thinness | < 16 |
| Moderate Thinness | 16 – 17 |
| Mild Thinness | 17 – 18.5 |
| Normal | 18.5 – 25 |
| Overweight | 25 – 30 |
| Obese Class I | 30 – 35 |
| Obese Class II | 35 – 40 |
| Obese Class III | > 40 |
BMI Calculator – Check Your Body Mass Index Instantly The BMI Calculator helps you find out if your weight is healthy for your height. Simply enter your age, gender, height, and weight, then click Calculate to see your BMI result. The BMI Calculator works in both US and Metric Units, and also shows your Ponderal Index for a more detailed assessment.
BMI introduction
BMI (Body Mass Index) is a number that estimates body fat based on your height and weight. The BMI Calculator classifies results into four main categories: Underweight, Normal, Overweight, and Obese. A healthy BMI range is typically 18.5 to 25.
BMI table for adults
This is the World Health Organization’s (WHO) recommended body weight based on BMI values for adults. It is used for both men and women, age 20 or older.
| Classification | BMI range – kg/m2 |
| Severe Thinness | < 16 |
| Moderate Thinness | 16 – 17 |
| Mild Thinness | 17 – 18.5 |
| Normal | 18.5 – 25 |
| Overweight | 25 – 30 |
| Obese Class I | 30 – 35 |
| Obese Class II | 35 – 40 |
| Obese Class III | > 40 |
BMI chart for adults
This is a graph of BMI categories based on the World Health Organization data. The dashed lines represent subdivisions within a major categorization.
BMI table for children and teens, age 2-20
The Centers for Disease Control and Prevention (CDC) recommends BMI categorization for children and teens between age 2 and 20.
| Category | Percentile Range |
| Underweight | <5% |
| Healthy weight | 5% – 85% |
| At risk of overweight | 85% – 95% |
| Overweight | >95% |
Understanding BMI Prime and Ponderal Index
The BMI Calculator also provides: BMI Prime – compares your BMI to the upper healthy limit (25). Ponderal Index (PI) – another indicator of body leanness, better for very tall or short people. Both values add more insight into your health beyond basic BMI results.
- High blood pressure
- Higher levels of LDL cholesterol, which is widely considered “bad cholesterol,” lower levels of HDL cholesterol, considered to be good cholesterol in moderation, and high levels of triglycerides
- Type II diabetes
- Coronary heart disease
- Stroke
- Gallbladder disease
- Osteoarthritis, a type of joint disease caused by breakdown of joint cartilage
- Sleep apnea and breathing problems
- Certain cancers (endometrial, breast, colon, kidney, gallbladder, liver)
- Low quality of life
- Mental illnesses such as clinical depression, anxiety, and others
- Body pains and difficulty with certain physical functions
- Generally, an increased risk of mortality compared to those with a healthy BMI
As can be seen from the list above, there are numerous negative, in some cases fatal, outcomes that may result from being overweight. Generally, a person should try to maintain a BMI below 25 kg/m2, but ideally should consult their doctor to determine whether or not they need to make any changes to their lifestyle in order to be healthier.
BMI Formula
The BMI Calculator uses these simple formulas: Metric Units: BMI=weight(kg)/height(m)2. US Units:BMI=703×weight(lbs)/height(in)2.For example, a person who is 5’10” (178 cm) and 160 lbs (72.5 kg) has a BMI of 23, which is in the Normal range.
Risks associated with being underweight
Being underweight has its own associated risks, listed below:
- Malnutrition, vitamin deficiencies, anemia (lowered ability to carry blood vessels)
- Osteoporosis, a disease that causes bone weakness, increasing the risk of breaking a bone
- A decrease in immune function
- Growth and development issues, particularly in children and teenagers
- Possible reproductive issues for women due to hormonal imbalances that can disrupt the menstrual cycle. Underweight women also have a higher chance of miscarriage in the first trimester
- Potential complications as a result of surgery
- Generally, an increased risk of mortality compared to those with a healthy BMI
In some cases, being underweight can be a sign of some underlying condition or disease such as anorexia nervosa, which has its own risks. Consult your doctor if you think you or someone you know is underweight, particularly if the reason for being underweight does not seem obvious.
Limitations of BMI
Although BMI is a widely used and useful indicator of healthy body weight, it does have its limitations. BMI is only an estimate that cannot take body composition into account. Due to a wide variety of body types as well as distribution of muscle, bone mass, and fat, BMI should be considered along with other measurements rather than being used as the sole method for determining a person’s healthy body weight.
In adults:
BMI cannot be fully accurate because it is a measure of excess body weight, rather than excess body fat. BMI is further influenced by factors such as age, sex, ethnicity, muscle mass, body fat, and activity level, among others. For example, an older person who is considered a healthy weight, but is completely inactive in their daily life may have significant amounts of excess body fat even though they are not heavy. This would be considered unhealthy, while a younger person with higher muscle composition of the same BMI would be considered healthy. In athletes, particularly bodybuilders who would be considered overweight due to muscle being heavier than fat, it is entirely possible that they are actually at a healthy weight for their body composition. Generally, according to the CDC:
- Older adults tend to have more body fat than younger adults with the same BMI.
- Women tend to have more body fat than men for an equivalent BMI.
- Muscular individuals and highly trained athletes may have higher BMIs due to large muscle mass.
In children and adolescents:
The same factors that limit the efficacy of BMI for adults can also apply to children and adolescents. Additionally, height and level of sexual maturation can influence BMI and body fat among children. BMI is a better indicator of excess body fat for obese children than it is for overweight children, whose BMI could be a result of increased levels of either fat or fat-free mass (all body components except for fat, which includes water, organs, muscle, etc.). In thin children, the difference in BMI can also be due to fat-free mass.
That being said, BMI is fairly indicative of body fat for 90-95% of the population, and can effectively be used along with other measures to help determine an individual’s healthy body weight.
Final
The BMI Calculator is a simple but powerful tool to monitor your weight and health. Use it regularly to ensure you’re within a healthy range and discuss your results with a doctor or nutritionist for personalized advice.