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An ideal weight calculator answers a question that has no single correct answer — what should I weigh? Enter your height, gender, and age, and it returns an estimate drawn from clinical formulas developed over the past sixty years. Those formulas were built for specific purposes: drug dosing, clinical assessment, actuarial risk analysis. None of them was designed as a universal health target. What they offer is a reference point, a range within which your weight is statistically associated with the lowest health risk. The more useful approach is to treat the calculator as a starting point, then layer in body composition, waist circumference, and how you actually feel.
The calculator runs your height and gender through one or more established formulas. Each formula returns a single number in kilograms or pounds. That number represents a weight that, for the average person of your height and sex, correlates with optimal health outcomes in the populations those formulas were derived from.
The formulas share a common structure: a base weight for a reference height (usually 5 feet or 152.4 cm), plus a fixed increment for every inch above that reference. The differences lie in the base weights and increments, which is why four formulas can produce results that differ by 5 kg or more for the same person.
Alongside the formula results, most calculators also display your healthy BMI range. That range is arguably the more defensible reference because it is derived from population-level data on mortality and disease risk. For a person of average build, the formula estimate will usually fall inside the BMI range. For someone who is very muscular or has a larger frame, it may fall outside it — and that is not necessarily a problem.
Four formulas dominate clinical and consumer use. Each has a distinct origin and a distinct set of coefficients.
The Devine formula was developed for calculating gentamicin dosage. It remains the most widely used in clinical settings, particularly for medication dosing where lean body weight matters. The equations are:
For a 5'10" (178 cm) man, the Devine formula returns 50 + (2.3 × 10) = 73 kg. For a 5'5" (165 cm) woman, it returns 45.5 + (2.3 × 5) = 57 kg.
Robinson and colleagues refined the Devine formula using actuarial data from life insurance tables. It tends to produce slightly lower estimates for men and slightly higher ones for women compared to Devine.
For the same 5'10" man, Robinson gives 52 + (1.9 × 10) = 71 kg. For the 5'5" woman, it gives 49 + (1.7 × 5) = 57.5 kg.
The Miller formula was published in the same year as Robinson, with a slightly different calibration. It uses a higher base weight and a smaller increment, which compresses the range of results across heights.
For the 5'10" man, Miller returns 56.2 + (1.41 × 10) = 70.3 kg. For the 5'5" woman, it returns 53.1 + (1.36 × 5) = 59.9 kg.
The Hamwi formula predates the others and was designed for quick clinical estimation. It is still used in eating disorder treatment protocols and nutritional assessment. Its increments are the largest of the four, so it produces the widest spread across heights.
For the 5'10" man, Hamwi gives 48 + (2.7 × 10) = 75 kg. For the 5'5" woman, it gives 45.5 + (2.2 × 5) = 56.5 kg.
| Height | Devine (M/F) | Robinson (M/F) | Miller (M/F) | Hamwi (M/F) |
|---|---|---|---|---|
| 5'5" (165 cm) | 62 / 57 kg | 61 / 57.5 kg | 63.3 / 59.9 kg | 64.5 / 56.5 kg |
| 5'7" (170 cm) | 66 / 61 kg | 65.3 / 60.4 kg | 66.1 / 62.6 kg | 69.3 / 60.9 kg |
| 5'9" (175 cm) | 71 / 66 kg | 69.1 / 64.4 kg | 68.9 / 65.3 kg | 74.1 / 65.3 kg |
| 5'11" (180 cm) | 75 / 71 kg | 72.9 / 68.4 kg | 71.7 / 68.0 kg | 78.9 / 69.7 kg |
Values are approximate and rounded. The spread between the highest and lowest formula for the same height and gender can exceed 5 kg. That spread is not an error — it reflects the different purposes for which the formulas were designed.
The World Health Organization defines a healthy BMI as 18.5 to 24.9 for adults. That range applies to both men and women and is used by health authorities across India, the United States, the United Kingdom, Canada, and Australia. To convert that BMI range into a weight range for your height, use the formula:
For a person who is 170 cm (1.70 m) tall, the healthy weight range is 18.5 × 1.70² = 53.5 kg to 24.9 × 1.70² = 72.0 kg. That is a range of 18.5 kg — roughly 40 pounds. That width is not a flaw. It is an honest reflection of how much healthy weight varies among people of the same height. Body frame, muscle mass, and fat distribution all influence where within that range a person's optimal weight falls.
For South Asian populations, the Indian Council of Medical Research recommends a lower upper limit. South Asians tend to develop metabolic risk — insulin resistance, type 2 diabetes, cardiovascular disease — at lower BMI values than Caucasian populations. The ICMR therefore recommends a healthy BMI range of 18.5 to 22.9 for Indians. For the same 170 cm person, that adjusted range is approximately 53.5 kg to 66.2 kg. If you are of South Asian descent, this narrower range is the more relevant reference.
| Height | WHO Range (kg) | ICMR Range (kg) |
|---|---|---|
| 150 cm (4'11") | 42–56 | 42–52 |
| 155 cm (5'1") | 44–60 | 44–55 |
| 160 cm (5'3") | 47–64 | 47–59 |
| 165 cm (5'5") | 50–68 | 50–62 |
| 170 cm (5'7") | 53–72 | 53–66 |
| 175 cm (5'9") | 57–76 | 57–70 |
| 180 cm (5'11") | 60–81 | 60–74 |
The ICMR range applies to South Asian adults. For other populations, use the WHO range. Both ranges assume an adult who is not pregnant and not engaged in high-level athletic training.
Body mass index is a ratio of weight to height. It tells you nothing about what that weight is made of. Muscle is denser than fat. A person with a high proportion of muscle can have a BMI that falls into the overweight category while carrying very little body fat. A person with a normal BMI can carry a high proportion of visceral fat — the metabolically active fat around the organs — and face elevated health risks.
This limitation is well documented in sports medicine. Research on elite athletes consistently shows that BMI misclassifies a substantial share of muscular individuals as overweight or obese, while athletes with low energy availability can present with unremarkable BMI values despite clinically significant issues[reference:0]. The problem is not that BMI is useless — it is a fast, cheap, and reasonably accurate screening tool for population-level risk. The problem is treating a screening tool as a diagnostic one.
If you are muscular, athletic, or have a body composition that falls outside the average, supplement BMI with other measures. Waist circumference is the most practical. A waist measurement above 90 cm for men or 80 cm for women indicates central adiposity, regardless of what the scale says. Body fat percentage, measured through DEXA, hydrostatic weighing, or a reliable bioelectrical impedance device, gives a more complete picture. A BMI calculator remains a useful first step, but it should not be the last.
The formulas produce different results for men and women because men and women differ in body composition at the same height. Men generally have more muscle mass and denser bones, which means a higher weight at the same height does not necessarily indicate excess fat. Women generally have a higher proportion of essential body fat, which serves reproductive and hormonal functions.
At the same BMI, women typically have a higher body fat percentage than men. A woman and a man of the same height and weight can have the same BMI but very different body compositions. This is why the formula-based ideal weight for a woman is lower than for a man at the same height. It is also why the healthy BMI range is the same for both sexes: the range accounts for these differences at the population level, even if individual variation is large.
The Devine, Robinson, Miller, and Hamwi formulas do not include age as a variable. They were derived from adult populations and are intended for adults. Age does influence body composition — muscle mass tends to decline after age 30, and fat mass tends to increase, even if total weight remains stable. That means an older adult at the same weight as a younger adult may have a higher body fat percentage and lower muscle mass.
For older adults, the focus shifts from weight to function. Maintaining muscle mass, bone density, and physical function matters more than hitting a specific number on the scale. A weight that falls slightly above the healthy BMI range may be protective in older age, particularly if it reflects preserved muscle mass rather than excess fat. The formulas do not capture this nuance, which is another reason to treat them as a reference point rather than a prescription.
None of these formulas applies to children or adolescents. Growth during childhood and adolescence follows a different trajectory, and body composition changes rapidly. Paediatricians use age- and sex-specific growth charts — such as those from the CDC or WHO — to assess whether a child's weight and height are tracking appropriately. Those charts plot percentiles, which allow comparison with a reference population. A child at the 50th percentile for weight is not "ideal" in any absolute sense; they are simply at the median for their age and sex.
If you are concerned about a child's weight, the correct tool is a growth chart interpreted by a paediatrician, not an adult ideal weight calculator.
The number the calculator returns is a reference, not a target. Here is how to use it sensibly.
First, look at the healthy BMI range, not just the formula estimate. The range is the more meaningful figure because it reflects the natural variation in healthy weight. If your current weight falls within that range and your waist circumference is within healthy limits, there is usually no medical reason to change your weight.
If your weight falls outside the range, direction matters more than distance. A sustained weight change of even 5% of body weight produces measurable improvements in blood pressure, blood sugar, and cholesterol. The goal is not to reach a specific number overnight — it is to move in a healthier direction at a sustainable pace. Health authorities in the UK, US, and India recommend a weight loss rate of 0.5 to 1 kg per week for safe, sustainable results.
If you are underweight, the priority is adding nourishing calories and building strength. If you are overweight, the priority is reducing energy intake and increasing physical activity. In both cases, the calorie calculator can help you estimate how much energy you need to maintain, lose, or gain weight, and the body fat calculator can give you a more detailed picture of your body composition.
It gives a reliable estimate based on height and gender, but it cannot account for muscle mass, bone density, or body composition. Two people of the same height can have very different healthy weights. Use the result as a starting point, not a definitive target.
The Devine, Robinson, Miller, and Hamwi formulas were developed at different times using different population data. Devine (1974) was designed for drug dosing, while Robinson and Miller (1983) refined it using actuarial data. They can differ by 5 kg or more for the same person, which is why no single number is the truth.
Yes. The formulas use different base weights and coefficients for men and women because men generally have more muscle mass and bone density at the same height. A woman's healthy weight range at a given height is typically lower than a man's.
The World Health Organization defines a healthy BMI as 18.5 to 24.9 for adults. A BMI below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or above is obese. For South Asian populations, the Indian Council of Medical Research recommends a lower upper limit of 22.9.
BMI is a useful screening tool but has real limitations. It cannot distinguish muscle from fat. A muscular athlete can register as overweight despite having low body fat. For a complete picture, combine BMI with waist circumference, body fat percentage, and other health markers.
Your weight sits within a range, not at a single point. If your BMI falls between 18.5 and 24.9 and your waist circumference is within healthy limits, you are likely in a good place. Energy levels, blood pressure, blood sugar, and fitness matter more than the number on the scale alone.
Using the Devine formula, a 5'5" (165 cm) woman has an ideal body weight of about 57 kg (126 lbs). The healthy BMI range for that height is roughly 50 to 68 kg (110–150 lbs). The formula result sits inside that range, but the range itself is the more useful reference.
No. These formulas are designed for adults. Children and adolescents need age- and sex-specific growth charts, such as those from the CDC or WHO, because their body composition changes rapidly during growth. A paediatrician should interpret those charts.
In the end, the most useful thing an ideal weight calculator does is not give you a number — it gives you a range. That range acknowledges what the formulas cannot: that healthy weight is personal, that muscle matters, that age changes composition, and that a single figure on a scale is a poor summary of a person's health. Use the ideal weight calculator to find your range, check your waist circumference and body fat percentage alongside it, and treat the result as one input among many. Your energy, your strength, your labs, and how you feel day to day will tell you more about your health than any formula ever could.