Ideal Weight Calculator

What "ideal body weight" means, and what it doesn't

"Ideal body weight" sounds like a personal goal, but the phrase has a narrower, more technical meaning. The four equations in the calculator above (Devine, Robinson, Miller and Hamwi) estimate a reference weight from height and sex alone. Most were developed or adopted to help clinicians dose medicines whose distribution in the body depends on lean mass rather than total weight. They aren't health targets, they ignore muscle and frame size, and they disagree with each other by several kilograms at the extremes of height.

The calculator shows all four results next to the World Health Organization's healthy BMI range so you can see the spread rather than a single falsely precise number. This guide explains where each formula came from, why they diverge, how BMI relates to them, how adjusted body weight is used, and how to interpret your results sensibly. It isn't medical advice; if you're thinking about changing your weight, talk to a doctor or registered dietitian.

How the calculator works

The calculator asks for three things: sex, height (in centimeters or feet and inches, between 120 and 230 cm) and, optionally, your current weight. From those it produces:

1. The healthy weight range for your height: 18.5 × height² to 24.9 × height², shown in kilograms and pounds.
2. The range of the four IBW formulas, from the lowest to the highest result, plus each formula individually. Devine's value is highlighted because it's the one most used clinically.
3. Your BMI and its category, if you entered a weight.
4. Adjusted body weight based on the Devine IBW, again only if you entered a weight.

If your height is under 5 ft (152.4 cm), the calculator warns you that the formulas were defined for heights of 5 ft and above. It still extends each formula's slope downward, subtracting weight for every inch below 5 ft, because that's how most published calculators behave, but the results are less reliable there.

Terms that are easy to confuse

Several weight measures sound alike but answer different questions.

• Ideal body weight (IBW) is a formula-based reference weight from height and sex. It is mostly used in medicine as a stand-in for lean body size.
• Healthy weight range is the band of weights that gives a BMI between 18.5 and 24.9 at your height. It's a population screening range, not a personal prescription.
• Adjusted body weight is a dosing weight that sits between IBW and actual weight for people well above their IBW.
• Lean body mass is everything except fat: muscle, bone, organs and water. It can only be estimated from height and weight; measuring it requires methods such as body-composition scans.
• Desirable weight, a phrase from the 1959 MetLife tables, is a historical term, now retired because people read it as a target.

When a doctor or pharmacist mentions "ideal weight," they usually mean IBW in this technical sense. When a fitness app mentions it, it often means a target within the healthy BMI range. The calculator shows both so you can see how they relate.

From insurance tables to bedside formulas

The modern idea of an ideal weight began with life insurance. According to a 2021 commentary in Clinical Nutrition ESPEN, the Metropolitan Life Insurance Company worked with the statistician Louis Dublin, who used measurements from about four million policyholders and treated longevity as the test of an "ideal" weight. Dublin classified frame size by elbow breadth and dropped age from the standards, which led to MetLife's national weight standards of 1942–43. Revised tables followed in 1959, based on mortality data from the Build and Blood Pressure Study, and again in 1983, when the weights rose slightly. The words "ideal" and "desirable" were eventually removed because people misread them.

The same commentary lists the data's weaknesses: some heights and weights were self-reported, people were measured in clothing, and insured people weren't representative of the whole population.

Simple bedside formulas came later:

Devine's equation, first published in a paper on gentamicin therapy, became the most widely used in pharmacy. The 2021 commentary notes that it rested on anecdotal observation rather than a published derivation, and that no development method has been reported for Hamwi's rule either. All four share the same structure: a base weight at exactly 5 ft (60 in, 152.4 cm) plus a fixed amount per inch. The calculator converts your height using the exact inch of 2.54 cm defined by the US National Institute of Standards and Technology.

Worked examples across the height range

The table below shows what each formula gives at five heights, alongside the weight at BMI 22 and the WHO healthy BMI range of 18.5 to 24.9.

Near average heights the formulas cluster within about 5 kg. At the extremes they fan out. For a 150 cm woman, Miller's answer is 8.5 kg above Devine's, because Miller starts from a higher base and a gentler slope. For a 198 cm man, Hamwi gives 96.9 kg and Miller 81.5 kg, a gap of more than 15 kg. Note also that the 150 cm woman is below 5 ft, where the formulas weren't designed to apply; the calculator still extends the slope downward, as most calculators do, but flags the result.

For context, US adults are measured at an average of 175.1 cm for men and 161.2 cm for women in the NHANES 2021–2023 survey, so the formulas behave best close to the average and worst for the shortest and tallest people.

The same examples in pounds

Hamwi's rule was written in pounds, and it's easiest to check by hand in those units. For a 5′10″ man it's 106 lb plus 6 lb for each of the 10 inches over 5 ft, or 166 lb. For a 5′4″ woman it's 100 lb plus 5 × 4 = 120 lb. The calculator converts using the exact international pound of 0.45359237 kg, so 166 lb becomes 75.3 kg. (The table above shows 75.5 kg for the 178 cm man because 178 cm is slightly more than 5′10″.) Devine's 73.2 kg for the same man is about 161 lb, and the healthy BMI range at 178 cm, 58.6–78.9 kg, is roughly 129–174 lb.

Why straight lines can't match BMI

The divergence isn't random. BMI is weight divided by height squared, so the weight that corresponds to any fixed BMI grows with the square of height. The IBW formulas grow in a straight line. A curve and a straight line can only agree over a short stretch.

You can see this in the slope. At a BMI of 22, each extra inch of height adds about 1.70 kg at 5 ft 0 in, but about 2.21 kg at 6 ft 6 in. Devine's constant 2.3 kg per inch is steeper than the BMI curve at every height in that range, so it runs low for short people and high for tall people relative to BMI. Robinson's and Miller's gentler slopes run the other way for tall men.

Peterson and colleagues, writing in the American Journal of Clinical Nutrition in 2016, quantified this. They report that Devine's equation aligns best with a BMI of 22.8 for men and 21.3 for women, and cite earlier work showing that IBW equations generally underestimate weight at shorter heights and overestimate it at taller heights. Their proposed fix is a single linear equation fitted to BMI itself:

• Metric: weight (kg) = 2.2 × BMI + 3.5 × BMI × (height in m − 1.5)
• US: weight (lb) = 5 × BMI + (BMI ÷ 5) × (height in inches − 60)

At BMI 22 the metric version simplifies to about 48.4 kg + 77 kg per meter above 1.5 m: roughly 70.0 kg at 1.78 m and 85.4 kg at 1.98 m, close to the true BMI-22 values in the table.

BMI: where it came from and what it measures

The calculator's healthy range uses BMI, and it helps to know its history. The ratio of weight to height squared was proposed by Adolphe Quetelet in the 1830s, according to the 2021 commentary. The name "body mass index" came from Ancel Keys and colleagues, whose 1972 paper in the Journal of Chronic Diseases compared several weight-for-height indices in 7,424 healthy men from 12 cohorts in five countries. They found weight ÷ height² slightly better than the alternatives at tracking body fat while staying independent of height, and favored it for its simplicity and its applicability to every population.

Today the CDC and WHO use the same adult cut-offs: underweight below 18.5, healthy weight from 18.5 to under 25, overweight from 25 to under 30, and obesity from 30 (with classes at 35 and 40). The CDC describes BMI as one potential health indicator that should be considered alongside other factors. BMI can't tell muscle from fat, and as noted in the calculator section above, a WHO expert consultation published in The Lancet in 2004 found that health risks begin at lower BMI values in many Asian populations.

Adjusted body weight, step by step

For people well above their IBW, some drug doses use an adjusted body weight:

Adjusted body weight = IBW + 0.4 × (actual weight − IBW)

The 0.4 factor comes from pharmacokinetic research on aminoglycoside antibiotics. Traynor, Nafziger and Bertino studied gentamicin and tobramycin in 1,708 patients and found that the ratio of total to ideal body weight predicted how the drug distributed in the body, from which they derived correction factors for underweight and overweight patients.

Example: a 178 cm man with a Devine IBW of 73.2 kg who weighs 100 kg has an adjusted body weight of 73.2 + 0.4 × 26.8 = 83.9 kg. This number exists for dosing calculations. It isn't a weight-loss goal.

Limitations to keep in mind

Every formula on this page shares the same blind spots:

• Body composition. Height and sex can't distinguish muscle from fat. A muscular athlete can sit above every IBW and BMI threshold with very little body fat.
• Frame size. MetLife's original tables adjusted for frame using elbow breadth; the bedside formulas don't.
• Age. People lose height and muscle with age, and none of the equations account for it.
• Ancestry. Body-fat distribution and health risk at a given BMI differ between populations.
• Very short and very tall people. Linear formulas are least reliable at the extremes, as the table shows.
• Children and pregnancy. None of these formulas apply. Children's weight is assessed with BMI-for-age percentiles on growth charts.

Using the results sensibly

Treat the calculator as a way to see a range, not a target. If the four IBW values and the BMI range overlap around your current weight, you're near the middle of what height-based formulas can say. If they don't, that's a reason to look at the bigger picture with a professional, including waist measurement, fitness, blood pressure and blood tests, rather than chasing a number.

To explore how weight changes body shape at your height, try the 3D body visualizer. To see how your height compares with others, use the height percentile calculator, or compare yourself with friends and famous people in the height comparison chart.