Ideal Weight Calculator

Why Ideal Weight Is a Range, Not a Number

The concept of “ideal weight” has a complicated history. When Dr. B.J. Devine published his formula in 1974, it was never intended to define the perfect weight for every human being. It was developed for pharmaceutical dosing calculations — determining how much medication to give a patient based on their estimated lean body mass. Over time, clinicians began using it as a general health reference, and the public adopted it as a goal-setting tool. The same is true for the Robinson, Miller, and Hamwi formulas.

The reality is that there is no single “ideal” weight for any given height and sex. Human bodies vary enormously in bone density, muscle mass, fat distribution, organ size, and overall frame. Two people of identical height and sex can be equally healthy at very different weights. This is why we show you four formulas and their range, rather than presenting a single number as gospel. The spread between the formulas — often 5-10 kg (10-22 lbs) — reflects the genuine scientific uncertainty about what “ideal” means.

The Four Formulas Explained

Devine (1974)is the most widely referenced formula. Originally published for gentamicin dosing, it calculates ideal weight as a base amount for 5 feet of height plus an increment for each additional inch. For men, the base is 50 kg plus 2.3 kg per inch over 5 feet. For women, the base is 45.5 kg plus 2.3 kg per inch. Despite being developed for drug dosing, it became the default “ideal weight” formula in medical practice.

Robinson (1983) refined the Devine formula with updated coefficients based on actuarial data from the Metropolitan Life Insurance Company. It uses a slightly higher base for both sexes but a lower per-inch increment, which produces somewhat different results at extreme heights. For men: 52 kg base plus 1.9 kg per inch. For women: 49 kg base plus 1.7 kg per inch.

Miller (1983) was published the same year as Robinson and takes a different approach. It uses the highest base weight (56.2 kg for men, 53.1 kg for women) but the lowest per-inch increment (1.41 kg for men, 1.36 kg for women). This means it tends to give higher ideal weights for shorter people and lower ideal weights for very tall people compared to the other formulas.

Hamwi (1964) is the oldest of the four. Published a decade before Devine, it was designed as a quick bedside estimate for clinical use. It has the highest per-inch increment (2.7 kg for men, 2.2 kg for women), which means it produces the highest ideal weights for tall individuals. While it is the least refined, it remains in use because of its simplicity and long track record.

Major Limitations of Ideal Weight Formulas

All four formulas share the same fundamental limitations, and understanding these limitations is arguably more important than the numbers themselves.

They ignore body composition.A person with 80 kg of lean muscle and 10% body fat has a very different health profile than someone at 80 kg with 30% body fat — but these formulas treat them identically. If you strength train regularly and carry significant muscle mass, you will likely exceed every formula's “ideal” weight, and that is perfectly healthy.

They ignore age.Body composition changes naturally with age. Muscle mass tends to decrease and fat mass tends to increase after about age 30. None of these formulas account for this. The “ideal” weight for a 25-year-old and a 65-year-old of the same height is presented as identical, which is an oversimplification.

They ignore frame size. People have small, medium, and large skeletal frames. Someone with broad shoulders, thick wrists, and a wide pelvis will naturally weigh more than someone with a narrow frame at the same height, even with identical body fat levels. The Metropolitan Life tables from the 1950s actually included frame size adjustments, but none of the four formulas here do.

They were developed from limited populations. These formulas were primarily derived from data on Caucasian populations in the mid-to-late 20th century. Body composition norms vary by ethnicity and genetics. Research has shown that health risks associated with weight differ across populations — for example, Asian populations face elevated metabolic risk at lower BMIs than European populations.

Body Composition Matters More Than Scale Weight

If you take one thing away from this page, let it be this: what your weight is made of matters far more than the number itself. Two key metrics that are more informative than ideal weight formulas are body fat percentage and waist-to-hip ratio.

Body fat percentage tells you how much of your total weight is fat tissue versus lean mass (muscle, bone, organs, water). For men, 14-24% body fat is considered healthy, with 6-13% being athletic. For women, 21-31% is healthy, with 14-20% being athletic. You can estimate body fat using the US Navy method (we have a body fat calculator for that), skinfold calipers, or more advanced methods like DEXA scans.

Waist-to-hip ratio and waist circumference are particularly important because they indicate visceral fat — fat stored around internal organs. Visceral fat is strongly associated with metabolic syndrome, type 2 diabetes, and cardiovascular disease. A waist circumference above 102 cm (40 in) for men or 88 cm (35 in) for women is considered a risk factor regardless of total body weight.

The Psychological Dimension

Ideal weight calculators can be psychologically loaded. Seeing a number that is significantly different from your current weight can trigger frustration, shame, or unhealthy behaviors. It is important to approach these numbers with the right mindset.

First, recognize that these formulas produce estimates, not verdicts. They do not define your health, your worth, or your fitness level. A formula cannot look at you, measure your cardiovascular fitness, assess your blood markers, or evaluate how strong and capable you are. It only knows your height and sex.

Second, if you are pursuing weight change, focus on the process rather than the destination number. Sustainable fat loss happens at about 0.5-1% of body weight per week. Sustainable muscle gain happens at about 0.25-0.5% of body weight per month for intermediates. These rates are much slower than social media suggests, but they produce lasting results. Crash dieting to reach an “ideal weight” as fast as possible typically leads to muscle loss, metabolic adaptation, and rebound weight gain.

Third, consider setting performance goals alongside or instead of weight goals. Being able to do 10 pull-ups, deadlift 1.5x your body weight, or run a 5K in under 25 minutes are concrete, empowering goals that naturally move your body composition in a healthy direction. The scale number follows from healthy behavior — not the other way around.

A Better Way to Set a Goal Weight

Rather than targeting a single number from one formula, consider this more comprehensive approach:

• Use the healthy BMI weight range (18.5-24.9) as a broad guideline for where your weight might reasonably fall.
• Use the formula average as one data point, not the data point.
• Measure your body fat percentage to understand what your weight is made of. A body fat percentage in the healthy range is more meaningful than hitting a specific scale number.
• Track waist circumference — it is one of the strongest predictors of metabolic health risk, and it is easy to measure at home with a tape measure.
• Consult a healthcare provider who can evaluate your blood pressure, blood lipids, blood sugar, and other markers that actually predict health outcomes.
• Focus on how you feel and perform — energy levels, sleep quality, strength, endurance, and daily function are more meaningful than any formula.

Frequently Overlooked Factors

Several factors that influence healthy weight are rarely discussed in the context of ideal weight calculators. Hydration status can swing your scale weight by 1-3 kg (2-6 lbs) in a single day. Glycogen stores — carbohydrate energy stored in your muscles and liver — account for roughly 0.5-2 kg (1-4 lbs) and fluctuate based on diet and exercise. Women experience cyclical weight fluctuations of 1-3 kg due to hormonal changes throughout the menstrual cycle.

These normal fluctuations mean that even if you somehow determined your true “ideal weight” down to the gram, your scale would not consistently read that number. Day-to-day weight measurements are noisy data. What matters is the trend over weeks and months, not what the scale says on any given morning. This is another reason why body composition metrics (body fat percentage, waist circumference, progress photos) provide more actionable information than scale weight alone.

The Bottom Line

Ideal weight formulas are useful as rough reference points, but they are not prescriptions. They were developed decades ago for specific clinical purposes, and they do not account for body composition, frame size, age, ethnicity, or individual variation. Use them as one input among many — alongside body fat percentage, waist circumference, blood markers, and how you feel — to form a complete picture of your health. The best “ideal weight” is the weight at which you are strong, energetic, sleeping well, and performing at your best.