Healthy Weight Calculator
This calculator computes a healthy body weight range based on a person's height and is most accurate for adults aged 18 or older.
What is a Healthy Weight?
Healthy body‑weight limits are derived from the Body‑Mass Index. By entering a height, the tool applies the standard BMI formula to outline the weight intervals that correspond to the various BMI categories. For adults 18 years or older, a BMI of 18.5–25 kg/m2 is generally regarded as normal. See the BMI Calculator for details, but remember that “healthy weight” is an estimate that ignores factors like muscle mass or bone density. While it works for most people, some individuals may fall outside the typical range and still be healthy, which usually requires a professional assessment.
Effects of Being Underweight, Overweight, and Obese
Underweight (BMI < 18.5):
Several factors can lead to a low body mass, including hereditary traits, insufficient nutrition, metabolic disorders, medication side‑effects, or chronic illness. Being underweight is linked to conditions such as hyperthyroidism, cancer, and tuberculosis, and may signal an underlying health problem. Research has shown that mortality among underweight individuals can be comparable to that of severely obese people. However, this relationship may be driven by disease‑related weight loss, and when no illness is present, the death risk may not be markedly higher than for those with a normal weight.
Insufficient body weight can also bring about fatigue, reduced stamina, weakened bones, and a compromised immune system that heightens infection risk. Moreover, people who are thin because they lack nutrient‑dense foods (as opposed to excessive exercise) may suffer from malnutrition, affecting both physical growth and mental development. In extreme cases, severe malnutrition forms such as kwashiorkor and marasmus may develop.
Specifically for women, being underweight due to an eating disorder can result in the absence of menstruation, infertility, and possible complications during pregnancy.
Overweight (BMI 25-30):
Carrying excess weight usually stems from consuming more calories than the body burns through metabolism and physical activity. Additional contributors include alcohol use, genetic predisposition, eating disorders, a sedentary routine, poor dietary choices, and chronic stress.
The health consequences of being overweight are still debated compared with obesity. Most experts agree that excess weight triggers many of the same problems as obesity, though usually to a milder degree. Some studies even report a slightly lower death rate for overweight individuals compared with those of normal weight.1 These findings have sparked discussion about whether a BMI of 25–30, currently labelled as overweight, might actually be optimal, while others stress that mortality alone does not capture health, noting the higher chances of diabetes, heart disease, and various cancers associated with extra weight.
Obese (BMI > 30):
Obesity typically arises from a combination of inadequate physical activity, excessive caloric intake, and genetic susceptibility. In rarer instances, primary genetic factors, hormonal disturbances from endocrine disorders, certain medications, or psychiatric conditions play a dominant role. Although lifestyle and dietary modifications can prevent most cases, the full spectrum of causes is not yet fully understood. While personal energy balance is a key component, broader societal measures are required, and there is no simple algorithmic fix.
Having obesity dramatically raises the likelihood of cardiovascular problems such as heart disease and stroke, as well as hypertension, type‑2 diabetes, musculoskeletal issues like osteoarthritis, and several cancers. It can also lead to obstructive sleep apnea and depression (or be a consequence of depression). Because of these numerous complications, obesity shortens life expectancy and is listed among the leading preventable causes of death worldwide.
Maintaining a Healthy Weight
Underweight, overweight and obesity each carry distinct health risks, yet their management often overlaps, involving adjustments to nutrition, physical activity, and, when needed, mental‑health support.
For those who are underweight, boosting caloric intake with nutrient‑dense foods—such as whole grains, vegetables, lean proteins, nuts and seeds—can promote healthy weight gain. Resistance training, like weight lifting, helps build muscle mass as well. When an eating disorder like anorexia or bulimia underlies the low weight, treatment must combine psychological therapy with nutritional and physical strategies.
Weight reduction for overweight and obese individuals largely depends on dietary changes and regular exercise. The WHO advises cutting back on high‑calorie foods, total fats, and added sugars, while increasing fruits, vegetables, legumes, whole grains, and nuts. It also recommends at least 60 minutes of daily activity for children and a total of 150 minutes per week for adults. Nonetheless, personal responsibility is most effective when people have access to education, affordable healthy foods, and policy measures such as sugary‑drink taxes, reduced sugar and salt in processed products, and limited marketing of unhealthy foods to youth.2
- Flegal, Katherine M., Graubard, Barry I., Williamson, David F., et al. 2017. "Excess Deaths Associated With Underweight, Overweight, and Obesity."The Journal of the American Medical Association 294(15): 1861-1867. doi:10.1001/jama.293.15.1861.
- World Health Organization (2021). “Obesity and Overweight.” Media Centre. Updated June 2021. https://www.who.int/mediacentre/factsheets/fs311/en/