Ideal Weight Calculator — Free 2026

Understanding Ideal Body Weight

Ideal body weight (IBW) is a clinical concept that estimates the weight range associated with the lowest risk of weight-related health complications for a person of a given height and sex. The concept originated in the mid-20th century when insurance companies and physicians sought simple ways to assess whether a patient's weight posed health risks. Over the decades, several formulas have been developed, each using slightly different approaches but all sharing the same core principle: a base weight for a height of 5 feet, with additional weight added for each inch above that baseline.

It is important to understand that ideal body weight is an estimate, not a definitive target. The formulas were developed using population-level data and do not account for individual differences in muscle mass, bone density, body fat distribution, age, or ethnicity. A bodybuilder and a sedentary office worker of the same height and sex would receive the same IBW result, despite having very different body compositions and health profiles. IBW should be used as one data point among many in assessing overall health.

The Four Formulas Explained

The Devine formula (1974) is the most widely referenced IBW equation, originally developed by Dr. B.J. Devine for calculating drug dosages based on body weight. For males, it calculates 50 kg plus 2.3 kg for each inch over 5 feet. For females, it starts at 45.5 kg plus 2.3 kg per inch over 5 feet. Despite being designed for pharmacological purposes, it became the de facto standard for general IBW estimation.

The Robinson formula (1983) was developed using Metropolitan Life Insurance actuarial data. It uses slightly different coefficients: 52 kg + 1.9 kg per inch over 5 feet for males, and 49 kg + 1.7 kg per inch over 5 feet for females. The Miller formula (1983) tends to produce the lowest estimates: 56.2 kg + 1.41 kg per inch for males and 53.1 kg + 1.36 kg per inch for females. The Hamwi formula (1964), one of the earliest, uses 48.0 kg + 2.7 kg per inch for males and 45.5 kg + 2.2 kg per inch for females.

Frame Size and Adjustments

Body frame size accounts for differences in skeletal structure. People with larger frames naturally carry more bone and muscle mass, meaning their healthy weight is higher than someone with a smaller frame at the same height. A common adjustment is to subtract 10% from the IBW for a small frame and add 10% for a large frame, with medium frame using the unadjusted value. You can estimate your frame size using the wrist test: wrap your thumb and middle finger around your opposite wrist. If they overlap, you likely have a small frame; if they just touch, a medium frame; and if there is a gap, a large frame.

For a more comprehensive view of your body composition, consider using our BMI calculator alongside this tool, or explore our body fat calculator for a direct estimate of your fat-to-lean ratio. Understanding your daily calorie needs can also help you work toward your ideal weight in a healthy, sustainable way.

Healthy BMI Weight Range

In addition to the four IBW formulas, this calculator shows the weight range corresponding to a BMI of 18.5 to 24.9 for your height. This BMI-based range is endorsed by the World Health Organization and the CDC as the general guideline for healthy weight. It provides an additional reference point to compare against the formula-based estimates. When the IBW formulas and the BMI range converge on a similar range, you can have greater confidence in the target. When they diverge, it may indicate that individual factors like frame size and body composition warrant closer attention.