Ideal Weight Calculator four formulas that disagree
Enter your height and sex. You get what each published formula suggests, and the weight range a healthy BMI implies at the same height.
A Reference Point, Not a Target
These are population formulas. None of them has met you.
Height and Sex Only
No formula here knows your build, your muscle mass or your health.
What is ideal body weight?
At a Glance
"Ideal body weight" is a clinical reference figure calculated from height and sex — originally for drug dosing and ventilator settings, not for personal goal setting. Four formulas are in common use, they disagree with each other by several kilograms, and the healthy range implied by BMI is wider than all four put together.
All four formulas share one shape: a base weight at five feet, plus a fixed amount for every inch above it. They differ only in those two constants.
male: 50 kg + 2.3 kg per inch over 5 ft · female: 45.5 kg + 2.3 kg per inchThe others adjust both constants: Robinson starts higher and climbs more slowly, Miller climbs slowest of all, and Hamwi climbs fastest. That is why the disagreement grows with height — at 178 cm the four span 4.8 kg, and at 190 cm they span 10.9 kg.
According to the clinical literature, Devine's formula was published as a rule of thumb for calculating drug doses rather than as a health target, and it has been used ever since largely because it is convenient. None of the four was derived from mortality or health outcomes.
The healthy range shown beside them comes from the WHO BMI categories instead:
weight = BMI × height² for BMI 18.5 to 24.9These are the values the calculator loads by default.
Find the height above five feet
178 cm − 152.4 cm = 25.6 cm, which is 10.08 inches.
Apply the Devine constants
50 kg + 2.3 × 10.08 = 73.2 kg.
Compare the other three
Robinson gives 71.1, Miller 70.4, Hamwi 75.2. The four span 4.8 kg.
Lay the healthy range over the top
A BMI of 18.5 to 24.9 at 178 cm is 58.6 to 78.9 kg — a 20 kg band that contains all four figures comfortably.
Watch the disagreement grow
At 190 cm the four run from 77.1 to 88.0 kg — 10.9 kg apart. The taller you are, the less any single formula means.
The most useful thing this page can tell you is how little a single "ideal weight" figure is worth.
Use the range, not the point. Any weight inside the healthy BMI band is, on population evidence, a reasonable place to be. A formula that names one number to a decimal place implies a precision that does not exist.
The formulas were built for dosing, not for goals. Devine's is still used to calculate drug doses and ventilator tidal volumes because a standardised number is needed for those tasks. That is a completely different job from telling an individual what to weigh.
They ignore body composition entirely. A muscular athlete at 178 cm can sit well above every one of these figures and be perfectly healthy, while someone at exactly 73.2 kg with very little muscle may not be. If you want a body-composition view, Body Fat Percentage Calculator and BMI Calculator are more informative together than either alone.
They ignore frame size. Hamwi's original method included a ±10 % adjustment for small and large frames, which most modern implementations drop. That alone is ±7 kg at 178 cm.
If you are planning a weight change, the Calorie Deficit Calculator turns a target into a timeline.
What these formulas cannot know
This calculator is for informational purposes and is not medical advice or a diagnosis.
- They use height and sex only. No muscle, no frame, no age, no history.
- They disagree, increasingly with height. 4.8 kg apart at 178 cm; 10.9 kg apart at 190 cm.
- They were not derived from health outcomes. These are dosing and reference formulas, not evidence-based health targets.
- They extrapolate badly below five feet, where the base weight is all that remains and the per-inch term turns negative.
- They assume a binary sex variable, which is how they were published; they do not accommodate everyone.
- A single "should" weight can be harmful framing. If weight is a source of distress, a range and a conversation with a professional serve better than a number.
Discuss any target weight with a doctor or a registered dietitian, particularly if you are managing a health condition, are pregnant, or have a history of disordered eating.