The Ideal Weight Calculator compares several classic height-based formulas and places them beside the weight range that corresponds to a healthy BMI for the same height. Enter height and sex, and the tool returns Devine, Robinson, Miller and Hamwi estimates together with the broader BMI-based span, so the spread between methods is visible rather than hidden.
No formula defines a healthy weight for a specific person. These equations disagree with each other by kilograms, and they were built for clinical dosing estimates rather than as life targets. This page shows the numbers plainly and treats the healthy-BMI weight range as the more meaningful framing, because a single "ideal" kilogram figure was never an honest answer.
Estimate an ideal weight range
Ideal-body-weight formulas take height and sex and return a single reference mass. Clinicians historically used those figures when scaling certain drug doses. Fitness sites later reused the same equations as if they described the weight a person ought to carry. The arithmetic is simple. The interpretation is where trouble starts.
The Ideal Weight Calculator runs four named formulas side by side and also inverts the adult healthy BMI band (18.5 to 25) into a weight range for the entered height. That range is usually wider than any one formula's point estimate, which matches how real healthy bodies vary. Adult formulas only; they are not validated as personal health targets.
The result is a set of reference numbers for general information. It is not a prescription, not a goal weight, and not medical advice. Where a person sits relative to any of these figures matters less than overall health, strength, habits and what a clinician sees in context.
Understand that no formula defines a healthy weight
This is the central claim on the page, and it is not a disclaimer tucked at the foot. No height-based equation, and no BMI band either, can state how much a specific person should weigh. Muscle mass, bone structure, fat distribution, age, medications and medical history all sit outside these formulas.
Devine, Robinson, Miller and Hamwi routinely disagree by several kilograms for the same height and sex. If four published equations cannot agree, none of them earns the status of a personal target. Framing any one result as "your ideal weight" turns a clinical shortcut into a verdict the maths never supported.
Healthy weight, when the phrase is used carefully, usually means a range associated with lower average risk in populations, not a single kilogram. The healthy-BMI span for a given height is shown here for that reason. Even that span is a screening guide. Two people in the same band can differ widely in fitness and metabolic health.
Compare the ideal weight formulas
All four formulas start from a base weight at 5 feet (152.4 cm) and add a fixed number of kilograms for each inch above that height. They apply to adults. Coefficients differ by sex and by author, which is why the outputs diverge.
| Formula | Male | Female |
|---|---|---|
| Devine (1974) | 50.0 + 2.3 × (inches over 60) | 45.5 + 2.3 × (inches over 60) |
| Robinson (1983) | 52 + 1.9 × (inches over 60) | 49 + 1.7 × (inches over 60) |
| Miller (1983) | 56.2 + 1.41 × (inches over 60) | 53.1 + 1.36 × (inches over 60) |
| Hamwi (1964) | 48.0 + 2.7 × (inches over 60) | 45.5 + 2.2 × (inches over 60) |
Source: Devine 1974, Robinson 1983, Miller 1983, Hamwi 1964, as listed in the site health reference. Inches over 60 means height in inches minus 60 (five feet). Someone shorter than 5 feet falls outside the usual domain of these particular equations as implemented here.
The calculator reports each result and the spread between the highest and lowest. That spread is the feature, not a bug: disagreement is evidence that a point target is the wrong product.
See your healthy BMI weight range
Inverting adult BMI categories gives a weight span for any height instead of a single target kilogram. Using the healthy band from 18.5 to 25 turns the familiar screening ratio into a practical mass range that many clinicians treat as a population guide rather than a personal order:
lower kg = 18.5 × height(m)²
upper kg = 25 × height(m)²For many heights that span is on the order of 15 to 25 kg. That width is intentional. Population guidelines describe a zone, not a bullseye. The Ideal Weight Calculator shows this range as the primary framing beside the four point formulas, because a zone matches the honesty of the topic better than a single "ideal" number.
BMI still cannot separate muscle from fat, so a muscular person may sit above the upper end while carrying little fat, and an older adult with low muscle may sit inside the band while composition is less favourable. The BMI Calculator page owns that discussion; here the range is borrowed as a clearer alternative to fake precision from dosing formulas.
Calculate ideal weight for a 180 cm adult
A single height shows how far the classic formulas diverge while the BMI-based span stays wide on purpose. Take an adult male who is 180 cm tall, then convert that height for the inch-based equations and for the healthy weight range.
1. Inches over 5 feet. 180 cm ÷ 2.54 ≈ 70.87 in 70.87 − 60 ≈ 10.87 in over 5 feet
2. Four formulas (male). Devine: 50.0 + 2.3 × 10.87 ≈ 75.0 kg Robinson: 52 + 1.9 × 10.87 ≈ 72.6 kg Miller: 56.2 + 1.41 × 10.87 ≈ 71.5 kg Hamwi: 48.0 + 2.7 × 10.87 ≈ 77.3 kg
3. Healthy BMI weight range at 1.80 m. 18.5 × 1.80² = 59.9 kg 25 × 1.80² = 81.0 kg
The four "ideal" figures span roughly 71.5 to 77.3 kg, a spread of about 5.8 kg among themselves, while the healthy-BMI band runs from about 60 to 81 kg. A person can sit anywhere in that wider band, or occasionally outside it for athletic reasons, without the formulas settling the question. The honest reading is the range plus clinical context, not the nearest point estimate.
Understand what these formulas are actually for
Devine, Robinson, Miller and Hamwi grew out of clinical need for a quick mass estimate when dosing certain medicines, especially in settings where body weight alone was a poor guide or hard to obtain cleanly. They were never validated as definitions of lifelong healthy weight, athletic weight or aesthetic targets.
Using a dosing reference as a personal goal confuses two jobs. A pharmacokinetic shortcut answers what mass to plug into a clinical calculation. A health conversation asks about energy balance, strength, labs, symptoms and sustainable habits. Those conversations do not reduce to one equation from 1964 or 1974.
When a clinician still uses ideal body weight in a dosing context, that decision belongs in the clinic with the full chart. This educational tool computes the classic formulas so the numbers are transparent, states that they disagree, and keeps the healthy-BMI range in view so the page does not pretend a single kilogram is destiny.
Frequently asked questions
Is there a formula that defines a healthy weight?
No. No ideal-weight formula, and no single BMI number, defines a healthy weight for a specific person. Formulas disagree with each other, and health depends on more than height-based arithmetic. A range plus clinical context is the honest framing.
Which ideal weight formula is most accurate?
None is validated as a personal health target. Devine is widely cited in clinical dosing contexts; Robinson, Miller and Hamwi are common alternatives. Accuracy for "what should someone weigh" is the wrong question for all of them.
Why do the formulas disagree?
Each author chose different base weights and increments per inch of height. Those modelling choices produce different outputs for the same person, often several kilograms apart. The disagreement is expected and informative.
What is a healthier way to read the result?
Prefer the healthy-BMI weight range for the entered height as a broad population guide, and treat the four point formulas as historical clinical estimates. Pair any number with how you feel, train, eat and what a doctor observes.
Do these formulas work for women and men the same way?
The structure is the same (base plus kilograms per inch over 5 feet), but coefficients differ by sex. Enter the sex that matches the formula set you want to compare. Interpretation limits are identical: still not a personal target.
What if current weight is outside every formula?
Many healthy, strong or recovering bodies sit outside classic ideal-weight point estimates. Being above or below Devine or Hamwi does not by itself define a problem or a success. Discuss concern with a clinician rather than chasing a formula.
Are ideal weight formulas useful for children?
No. These adult height-based equations are not the right tool for anyone still growing. Paediatric weight assessment uses growth charts and clinical judgement, not Devine-style targets.
How does this relate to BMI?
BMI converts height and weight into a ratio with adult category bands. Ideal-weight formulas invent a reference mass from height alone. This page shows both lenses and still insists that neither defines individual healthy weight.
What if height is under 5 feet?
The classic equations add kilograms for each inch above 60 inches (152.4 cm). Below that height the usual increment model does not apply in the same way, and this tool's adult formulas are a poor fit. A clinician or the healthy-BMI framing for that height is the safer reference.
Should weight be forced toward Devine or Hamwi?
No. Chasing a single formula kilogram is the opposite of the page's point. Prefer sustainable habits, strength and clinical context over matching any one 1970s coefficient set.
Summary
The Ideal Weight Calculator compares Devine, Robinson, Miller and Hamwi for an entered height and sex, shows how far they disagree, and foregrounds the healthy-BMI weight range (BMI 18.5 to 25 inverted for that height). No formula defines a healthy weight for a specific person; these equations began as clinical dosing aids, not life targets.
Read the outputs as reference estimates for general information, not as a goal or a judgement, and take health decisions with broader context and professional input.