Wondering what your ideal body weight should be? This free ideal weight calculator runs all four classical IBW formulas — Devine, Robinson, Miller, and Hamwi — and shows the average, so you don't have to pick just one. It also shows the WHO healthy BMI range (18.5–24.9), which most modern dietitians prefer over a single magic number. Choose male or female, type your height in cm or feet+inches, and get an answer in kg or pounds.
Ideal body weight (IBW) is an estimate of the weight a person 'should' be, based primarily on their height. The concept comes from clinical medicine — doctors needed a standardized weight to calculate drug doses safely, and a real measured weight wasn't always available. Dr. B. J. Devine first published the formula now bearing his name in a 1974 paper on gentamicin dosing. Three other formulas followed — Robinson (1983), Miller (1983), and Hamwi (1964) — each tweaking the intercept and slope slightly. None is 'right' in any absolute sense; they're all rough estimates derived from population averages. Modern guidance leans toward the WHO BMI healthy range (18.5–24.9) instead, but the classical formulas remain in use, especially for medication dosing.
Every classical IBW formula has the same shape — a base weight, plus an extra amount per inch over 5 feet. They just disagree on the numbers.
Devine, Robinson, Miller, and Hamwi all use height as the sole anthropometric input. No age, no body composition, no activity level. This is by design — they were built to be calculable from a single measurement at the bedside.
Each formula has a slightly lower base for women than men, reflecting the population average that women have somewhat less lean body mass per unit height. The difference is around 3–5 kg in the base, with similar per-inch slopes.
All four are simple linear formulas: every extra inch adds a fixed amount of kg. This is a known simplification — real lean body mass scales sub-linearly with height, so very tall people often weigh less than the formula predicts and very short people more.
The formulas were derived from population samples — predominantly white, predominantly American, mostly 20th-century. They're estimates of where the average healthy adult of your height sits, not a personalized target. Treat the number as a reference point, not a goal.
The four classical formulas usually agree within 2–3 kg, but the spread widens at the extremes. Devine sits in the middle and is the most cited clinically; Hamwi tends to give the highest numbers; Miller the lowest.
| Height | Devine ♂ | Robinson ♂ | Miller ♂ | Hamwi ♂ | Avg ♂ | Avg ♀ |
|---|---|---|---|---|---|---|
| 155 cm (5'1") | 61.5 kg | 55.7 kg | 60.6 kg | 55.5 kg | 58.3 kg | 53.9 kg |
| 160 cm (5'3") | 65.9 kg | 59.5 kg | 63.4 kg | 60.8 kg | 62.4 kg | 57.7 kg |
| 165 cm (5'5") | 70.4 kg | 63.3 kg | 66.2 kg | 66.1 kg | 66.5 kg | 61.6 kg |
| 170 cm (5'7") | 74.9 kg | 67.1 kg | 69.0 kg | 71.4 kg | 70.6 kg | 65.4 kg |
| 175 cm (5'9") | 79.4 kg | 70.9 kg | 71.8 kg | 76.7 kg | 74.7 kg | 69.2 kg |
| 180 cm (5'11") | 83.9 kg | 74.7 kg | 74.6 kg | 82.0 kg | 78.8 kg | 73.0 kg |
| 185 cm (6'1") | 88.4 kg | 78.5 kg | 77.4 kg | 87.3 kg | 82.9 kg | 76.8 kg |
| 190 cm (6'3") | 92.9 kg | 82.3 kg | 80.3 kg | 92.6 kg | 87.0 kg | 80.7 kg |
All four follow the same pattern: a base weight, plus a per-inch increment above 5 feet (60 inches). Only the constants differ. Here they are exactly as published.
Dr. B. J. Devine published this in a 1974 Drug Intelligence paper on gentamicin dosing. It became the default IBW formula in clinical practice and is still embedded in FDA drug-dosing guidance. The intercepts are the lowest, but the per-inch slope is the highest, so it gives mid-range numbers at average heights and the highest numbers at tall heights.
Male, 5'10" (70 inches): 50 + 2.3 × 10 = 73 kg. Female, 5'5" (65 inches): 45.5 + 2.3 × 5 = 57 kg.
Robinson et al. revisited Devine's formula in 1983 and found a slightly higher intercept but lower slope fit population data better. The result: at 5'10", Robinson gives ~71 kg vs Devine's 73 kg. The gender split is also wider than Devine's (3 kg male vs female base).
Male, 5'10" (70 inches): 52 + 1.9 × 10 = 71 kg. Female, 5'5" (65 inches): 49 + 1.7 × 5 = 57.5 kg.
Also from 1983, Miller's formula has the highest base but the lowest per-inch slope. It produces the most conservative estimates at tall heights — at 6'3", Miller gives 80 kg vs Devine's 93 kg. Best suited for short to average heights; significantly undershoots for very tall people.
Male, 5'10" (70 inches): 56.2 + 1.41 × 10 = 70.3 kg. Female, 5'5" (65 inches): 53.1 + 1.36 × 5 = 59.9 kg.
The oldest of the four, published by Dr. George Hamwi in 1964 in an American Diabetes Association manual. Originally meant for diabetic diet planning. Has the steepest male slope (2.7 kg/in), giving the highest male numbers at tall heights. Still widely used in clinical nutrition for menu planning.
Male, 5'10" (70 inches): 48 + 2.7 × 10 = 75 kg. Female, 5'5" (65 inches): 45.5 + 2.2 × 5 = 56.5 kg.
The classical formulas give a single number. The WHO BMI range gives you a band. Most current clinical guidelines lean toward the BMI range — it's more honest about the uncertainty, doesn't depend on the somewhat-arbitrary gendered intercepts of the old formulas, and matches the way modern epidemiology actually defines 'healthy weight.'
Devine, Robinson, Miller, Hamwi — each gives one weight, based on height and sex. Useful when you need a target for things like drug dosing, parenteral nutrition, or ventilator tidal-volume settings (the FDA still references Devine for IBW in dosing guidance).
BMI 18.5–24.9 = 'normal' or 'healthy' weight per WHO classification. For a 175 cm person, that's 57–76 kg — a 19 kg range. Wider than a single number, but more honest about the fact that healthy weight depends on muscle, frame, and many factors a single equation can't capture.
| Height | Devine ♂ | Devine ♀ | BMI healthy range |
|---|---|---|---|
| 160 cm | 65.9 kg | 61.4 kg | 47.4 – 63.7 kg |
| 170 cm | 74.9 kg | 70.4 kg | 53.5 – 71.9 kg |
| 180 cm | 83.9 kg | 79.4 kg | 59.9 – 80.7 kg |
| 190 cm | 92.9 kg | 88.4 kg | 66.8 – 89.9 kg |
A printable reference table. Average of the four classical formulas (Devine, Robinson, Miller, Hamwi), plus the WHO BMI healthy range for that height. Use it as a sanity check on whatever number the calculator gives you.
| Height | IBW (male) | IBW (female) | BMI healthy range |
|---|---|---|---|
| 150 cm (4'11") | 53.5 kg / 118 lb | 49.0 kg / 108 lb | 41.6 – 56.0 kg |
| 155 cm (5'1") | 58.3 kg / 129 lb | 53.9 kg / 119 lb | 44.4 – 59.8 kg |
| 160 cm (5'3") | 62.4 kg / 138 lb | 57.7 kg / 127 lb | 47.4 – 63.7 kg |
| 165 cm (5'5") | 66.5 kg / 147 lb | 61.6 kg / 136 lb | 50.4 – 67.8 kg |
| 170 cm (5'7") | 70.6 kg / 156 lb | 65.4 kg / 144 lb | 53.5 – 71.9 kg |
| 175 cm (5'9") | 74.7 kg / 165 lb | 69.2 kg / 153 lb | 56.7 – 76.2 kg |
| 180 cm (5'11") | 78.8 kg / 174 lb | 73.0 kg / 161 lb | 59.9 – 80.7 kg |
| 185 cm (6'1") | 82.9 kg / 183 lb | 76.8 kg / 169 lb | 63.3 – 85.2 kg |
| 190 cm (6'3") | 87.0 kg / 192 lb | 80.7 kg / 178 lb | 66.8 – 89.9 kg |
At the same height, the classical formulas give women an ideal weight 3–5 kg lower than men. That's not arbitrary — it reflects real average differences in body composition. But the operative word is 'average,' and the gap is smaller than people often assume.
Adult men average ~40% skeletal muscle, ~15% essential body fat, and higher bone density than women. Per unit height, men carry more lean mass — which weighs more than fat. That's why the male intercept in every IBW formula is higher.
Adult women average ~30% skeletal muscle and ~12% essential body fat (the minimum for reproductive and hormonal function). Lower bone density and proportionally smaller muscle mass mean less weight per unit height — hence the lower intercept.
| At 170 cm height | Male IBW (avg) | Female IBW (avg) | Gap |
|---|---|---|---|
| Devine | 74.9 kg | 70.4 kg | 4.5 kg |
| Robinson | 67.1 kg | 65.0 kg | 2.1 kg |
| Miller | 69.0 kg | 66.5 kg | 2.5 kg |
| Hamwi | 71.4 kg | 66.5 kg | 4.9 kg |
The classical IBW formulas assume an 'average' frame. In reality, frame size — measured by elbow breadth or wrist circumference — adjusts ideal weight by about ±10%. Here are two real-world examples to show how much it matters.
165 cm tall, 5'5"
165 cm tall, 5'5"
IBW isn't just a curiosity. It's used in several specific clinical and athletic contexts where a target weight is needed for decision-making.
Some medications — especially aminoglycoside antibiotics (gentamicin, tobramycin), chemotherapy drugs, and anesthetics — are dosed based on IBW, not actual weight. This is because the drugs distribute mainly into lean tissue, not fat. The Devine formula is still the FDA-referenced standard here.
Tidal volume in mechanically ventilated patients is set as 6 mL/kg of IBW, not actual weight. Using actual weight would over-inflate the lungs of obese patients (whose lung size is determined by height, not weight). Devine's formula is the ICU standard.
Registered dietitians use IBW (typically Hamwi or BMI midpoint) to set calorie and protein targets, especially for clinical nutrition — diabetes management, eating disorder recovery, parenteral nutrition. The IBW gives a metabolic baseline that doesn't change with day-to-day weight fluctuations.
Athletes and serious recreational lifters use IBW or BMI range as a sanity check, not a target. A 180 cm bodybuilder may weigh 95 kg with low body fat — well 'above' IBW but optimally healthy. Body composition (% body fat, fat-free mass index) is the metric that matters, not weight alone.
If you're a healthy adult looking for guidance, the WHO BMI healthy range (18.5–24.9) is a better answer than any single IBW formula. Aim to be anywhere in that range — exactly where in the range depends on your build, fitness, and goals, not the formula.
Measure your wrist with a soft tape. For women: under 14 cm = small frame, over 16.5 cm = large. For men: under 16.5 = small, over 19 = large. Adjust IBW by ±10% accordingly. This single adjustment is more impactful than picking which formula to use.
If you regularly lift heavy weights or compete in strength sports, IBW and BMI both lie. A 100 kg lifter at 12% body fat is healthier than a 75 kg sedentary person at 32%. Use a body fat percentage measurement (DEXA, calipers, or even circumference-based estimates) instead.
Whatever method you use, the trajectory matters more than the snapshot. Weight gain or loss of >5% per year is worth investigating (and is far more informative than whether you're 2 kg above or below 'ideal'). Track over months, not days.
The thresholds for diagnosing overweight (BMI 25) and obesity (BMI 30) are population-level cutoffs. For YOU specifically, what matters is whether you have metabolic markers (blood pressure, lipids, glucose) consistent with your weight category. A doctor can interpret 'are you actually at risk' way better than a calculator can.
The classical IBW formulas were designed for clinical dosing, not as personal weight goals. A normal range of 4–5 kg around the calculated number is biologically meaningless. Trying to hit 73 kg vs 72 kg accomplishes nothing.
If you're heavier than you'd like to be, Hamwi gives the highest male numbers — easy to find a formula that 'agrees' with where you are. This is confirmation bias. The average of all four is a better baseline; better still, use the WHO BMI range.
Two people of the same height and sex can have legitimately different ideal weights — different frames, different muscle mass, different body fat percentages. The fact that your friend 'should' weigh 65 kg and you 'should' weigh 65 kg doesn't mean you should weigh the same.
All four classical formulas are calibrated for adults 18+. They badly mis-predict for children, teens, and adolescents during growth phases. For people under 20, use age- and sex-specific BMI percentiles from CDC growth charts instead.
IBW is a function of height. Two people of the same height can have radically different body compositions — one 30% fat, one 12% fat — and the formula treats them as identical. If you care about health, weight alone is a poor proxy. Get a body composition measurement once and recalibrate your expectations.
Average of the four classical formulas: 61.6 kg (136 lb). Range across the formulas: 56.5 kg (Hamwi) to 64.4 kg (Devine). WHO BMI healthy range for 5'5" (165 cm): 50.4–67.8 kg (111–149 lb). So anywhere from ~111 lb to ~150 lb is 'healthy' depending on build.
Average of the four classical formulas: 72.4 kg (160 lb). Range: 70.3 kg (Miller) to 75 kg (Hamwi). WHO BMI healthy range for 5'10" (178 cm): 58.6–78.9 kg (129–174 lb). So anywhere from ~129 lb to ~174 lb is 'healthy' depending on build and muscle mass.
Neither is 'accurate' in any strict sense — both ignore body composition. BMI is preferred today because it gives a range rather than a single number, and it doesn't make assumptions about sex that may not apply to an individual. Devine remains the standard for drug dosing because it gives a single deterministic number, which is what dosing equations need.
'Ideal' is one number from a 1960s-1980s formula. 'Healthy' is a range — typically the WHO BMI 18.5–24.9 band — that captures the fact that human bodies vary. In casual conversation people use the terms interchangeably. In clinical conversation, 'healthy weight' = within BMI range; 'ideal weight' = a calculated single number for dosing or planning purposes.
Yes. Many athletes — distance runners, dancers, gymnasts — are below the classical IBW or BMI 18.5 and metabolically fine. Naturally lean adults also exist. The threshold flag (BMI < 18.5) is a population-level cutoff, not a personal one. What matters is your menstrual function (women), energy availability, bone density, and metabolic markers — not the scale.
Because there are four legitimate formulas and they disagree. At 5'9" male, Devine says 73 kg, Robinson says 70 kg, Miller says 70 kg, Hamwi says 72.6 kg. A 3 kg spread between formulas is normal. Different calculators online pick different defaults — some show Devine only, some average all four, some use BMI range. Always check which formula a tool uses.
None of them, strictly. All four classical formulas (Devine, Robinson, Miller, Hamwi) date from 1964–1983 and were derived from population averages of mostly-white, mostly-American adults. They don't account for muscle mass, frame size, ethnicity, or age. For most healthy adults, the WHO BMI healthy range (18.5–24.9) is a better single answer because it gives you a range, not a magic number. The Devine formula is most cited clinically because it's still used in FDA dosing guidelines, but 'most cited' doesn't mean 'most accurate'.
Men: 50 kg + 2.3 kg for every inch over 5 feet. Women: 45.5 kg + 2.3 kg for every inch over 5 feet. So a 5'10" (178 cm) man has an IBW of 50 + 2.3 × 10 = 73 kg. A 5'5" (165 cm) woman has an IBW of 45.5 + 2.3 × 5 = 57 kg. Originally published by Dr. B. J. Devine in 1974 as a tool for calculating gentamicin doses, it became the de facto clinical IBW formula and is still embedded in FDA dosing guidance today.
Ideal weight (from the classical formulas) is a single number based on your height and sex. BMI healthy weight is a RANGE of weights that put you in the WHO 'normal' BMI band (18.5–24.9). For a 175 cm person, classical IBW gives ~72 kg as one number; BMI range gives 57 kg to 76 kg. Modern dietitians and physicians overwhelmingly prefer the BMI range — a healthy weight is more like a band than a point, and the band is the same regardless of sex (the gendered intercepts in the old formulas reflect assumptions, not biology).
Because they were derived from population data showing that, on average, men have more lean body mass per unit height than women — more muscle, larger bone density, less essential body fat. The female intercepts in Devine, Robinson, Miller, and Hamwi are all 3–5 kg lower than the male intercepts to reflect that average. But it's a population average, not a personal target: a muscular female athlete will exceed the female IBW just from lean mass, and a sedentary male might fall below the male IBW without being underweight.
No — and this is the biggest known limitation. All four classical formulas and BMI itself misclassify highly muscular people as 'overweight' because muscle weighs more than fat. A 180 cm bodybuilder can easily weigh 95 kg with 8% body fat (extremely healthy) but score 'overweight' on BMI (BMI 29.3). For athletes, body composition (body fat percentage, lean mass index) is a much better metric than IBW or BMI. Use this calculator for general guidance, not as a target.
The classical formulas don't account for age — Devine gives the same number for a 25-year-old and a 75-year-old. In reality, evidence suggests slightly higher BMI ranges (around 22–27 instead of 18.5–24.9) may be associated with the lowest mortality in adults over 65. But this is debated in the literature. Bottom line: for adults 18–64, use the standard ranges. For seniors, treat 'a bit above' the healthy band as potentially fine — and talk to a physician rather than chasing a number.
Yes, 100% free, no signup, no tracking. All calculations run entirely in your browser using the formulas as originally published — Devine (1974), Robinson (1983), Miller (1983), Hamwi (1964), plus the WHO BMI categories. We never store your height, weight, or any other input.
For most adults 18–64, a healthy weight is anywhere in the WHO BMI range of 18.5–24.9. In kilograms: at 160 cm that's 47–64 kg; at 170 cm it's 53–72 kg; at 180 cm it's 60–81 kg. In pounds: at 5'4" (163 cm) that's 105–145 lb; at 5'8" (173 cm) it's 121–168 lb; at 5'11" (180 cm) it's 132–179 lb. The range is wide because 'healthy' depends on body composition, fitness, and personal context — not a single magic number.
Every formula in this calculator is implemented exactly as originally published. Devine's intercepts (50 kg male, 45.5 kg female) and per-inch slope (2.3 kg/in) come from his 1974 paper. Robinson, Miller, and Hamwi constants likewise. The WHO BMI healthy range (18.5 ≤ BMI ≤ 24.9) is from the WHO consultation reports of 1997 and 2000. We do not modify, average, or extrapolate the original formulas. All numbers shown match what you'd get computing by hand with the original references.