Ideal Weight Calculator

Find the healthy weight range for your height

Healthy weight is often expressed as a range rather than a single number, because many factors besides weight determine health. This calculator shows the BMI-based healthy weight range (BMI 18.5–24.9) for your height, along with estimates from three scientific formulas: Robinson (1983), Devine (1974), and Miller (1983).

Why a range beats a single number

Presenting a range rather than one target number is deliberate: it reflects the genuine scientific uncertainty in translating height alone into a health recommendation, and it avoids the false precision of implying that one specific kilogram figure is meaningfully healthier than a kilogram either side of it. A range also sits more comfortably with how bodies actually vary — frame size, muscle mass and build differ enormously between two people of identical height, and a sensible range accommodates that variation far better than a single number pretending to apply equally to everyone.

The BMI-based range

Body Mass Index (BMI) is calculated as weight in kilograms divided by height in metres squared. The World Health Organization defines the following BMI ranges:

• Under 18.5: Underweight
• 18.5–24.9: Normal/healthy weight
• 25.0–29.9: Overweight
• 30.0+: Obese

For a given height, the healthy weight range is the range of weights that produce a BMI between 18.5 and 24.9. For example, a person 170 cm tall has a healthy range of approximately 53.5–72.0 kg.

A worked example

Consider a woman who is 165 cm tall. Converting to the imperial units the classic formulas use, that is 5 feet and roughly 5 inches. Under the BMI-based range, her healthy weight spans approximately 50.4 to 67.8 kg. The Robinson formula estimates 49 + 1.7 × 5 = 57.5 kg. The Devine formula estimates 45.5 + 2.3 × 5 = 57 kg. The Miller formula estimates 53.1 + 1.36 × 5 = 59.9 kg. All three single-figure estimates cluster closely together and sit comfortably within the wider BMI-based range, which is typically how the numbers relate to one another: the named formulas tend to converge on a value somewhere in the middle of the broader healthy range rather than at either extreme.

Other ideal weight formulas

The BMI-based range gives a span of healthy weights, but several formulas have been developed to estimate a single "ideal" weight for a given height:

Robinson formula (1983): For men: 52 kg + 1.9 kg per inch over 5 feet. For women: 49 kg + 1.7 kg per inch over 5 feet.

Devine formula (1974): For men: 50 kg + 2.3 kg per inch over 5 feet. For women: 45.5 kg + 2.3 kg per inch over 5 feet. Originally developed for drug dosing in clinical settings.

Miller formula (1983): For men: 56.2 kg + 1.41 kg per inch over 5 feet. For women: 53.1 kg + 1.36 kg per inch over 5 feet.

These formulas all give slightly different results because they were derived from different population datasets using different statistical methods.

Limitations of weight-based health measures

BMI and ideal weight formulas have well-known limitations:

• They do not account for body composition (muscle vs. fat)
• They were derived primarily from white European populations and may be less accurate for other ethnic groups
• They do not distinguish fat distribution (abdominal fat is more harmful than fat elsewhere)
• They are less useful for children, elderly, and athletes

Additional measures like waist circumference, waist-to-height ratio, and body fat percentage provide more complete pictures of health status.

How to use the calculator

Enter your height and sex, and the calculator shows the BMI-based healthy weight range for that height alongside the single-figure estimates from the Robinson, Devine and Miller formulas. Rather than treating any one number as a strict target, use the spread across all four estimates as a rough sense of the range that clinicians and researchers have historically considered reasonable for someone of your height, and weigh that against your own body composition, activity level and how you actually feel.

Why the formulas disagree with each other

Each of the three named formulas was built by fitting a simple linear relationship to a specific dataset of the time, and those datasets differed in the populations sampled, the era they were collected in, and the statistical methods used to fit the line. The Devine formula in particular was created for a very specific clinical purpose — estimating a reasonable body weight for calculating medication dosages — rather than as a general wellness target, which is worth remembering before treating its output as a personal goal. None of the three formulas is more "correct" than the others in an absolute sense; they simply represent different historical attempts at the same rough estimation problem, which is exactly why looking at the range they collectively produce is more informative than fixating on any single one.

Using the result sensibly

Treat any figure from this calculator as one data point among several, not a verdict. A person's health depends on far more than a single ideal-weight number, including their muscle mass, waist circumference, fitness level, family history and how they actually feel day to day. If your weight sits outside the range shown here, that is worth a closer look rather than alarm, and a conversation with a doctor who can weigh up the fuller picture will always tell you more than any formula can on its own, no matter how many decimal places it produces.

Private and instant

All calculations run entirely in your browser, so results appear instantly and none of your personal height, weight or sex information is ever sent to a server, logged or shared.