Ideal Weight Calculator

Ideal body weight (IBW) formulas weren't originally created to define an aesthetic or fitness goal — they were developed to help estimate safe medication dosages, since the way many drugs metabolize in the body correlates more closely with IBW than with total body weight. Sports also use IBW-style weight classifications for competition categories. The formulas were never intended as a target to visually strive toward, even though that's how the term often gets used today.

Each formula was developed independently, by different researchers, using different reference populations and study data, at different points across the 20th century. The Devine formula (1974) is the most widely used today and the one most modern medical dosage calculations still default to. Robinson (1983) and Miller (1983) were both explicitly built as modifications of Devine's original formula, adjusting the per-inch weight increment based on newer research, which is why all four cluster somewhat closely but don't match exactly.

Devine is the most widely used and cited in clinical and pharmacological contexts today, which makes it a reasonable default if you need to pick just one. That said, no single formula is definitively "correct" — they're all population-average estimates based on height and sex alone, and the differences between them are usually smaller than the natural variation in what's healthy for any individual. Looking at the full range across all four formulas, alongside the healthy BMI weight range, gives a more honest picture than fixating on one number.

Because they were built using only height and sex as inputs, deliberately excluding body composition to keep the formulas simple and broadly applicable across a population. This is also their biggest limitation: a heavily muscled, lean athlete can show as "overweight" by IBW standards purely because muscle is denser than fat, not because they're carrying excess body fat. If body composition matters for your specific question, IBW formulas aren't the right tool — a body fat percentage measurement is far more informative.

Not directly in any of these formulas, and there's limited reason it should for adults — height and by extension IBW is largely stable from the late teens through most of adulthood. What does change with age is body composition: lean muscle mass tends to decline gradually over time, and it becomes easier to accumulate excess body fat at the same total weight. There's also a well-documented tendency to lose modest height (roughly 1.5-2 inches on average by age 70), which very slightly lowers the IBW these formulas would calculate for an older adult versus their younger self.

The WHO's healthy BMI range spans 18.5 to 25, which at any given height translates into a fairly wide span of acceptable weights — often 40-50+ pounds between the low and high end for an average adult height. The four named formulas (Devine, Robinson, Miller, Hamwi) each calculate a single point estimate instead, which is why they tend to land somewhere within that wider healthy BMI range rather than matching its lower or upper bound exactly.

Not necessarily, and definitely not as a hard target. These formulas are reference points built from population averages, not a personalized prescription — it's entirely possible to sit above or below your calculated IBW and be perfectly healthy, particularly if the difference comes from muscle mass, bone density, or body frame size rather than excess fat. Sustainable healthy habits — regular activity, a varied diet, adequate sleep — matter more for long-term health outcomes than chasing a specific number from any single formula.