What Is "Ideal Weight" and How Is It Calculated?
Ideal body weight formulas were originally developed in clinical and pharmaceutical settings — not as fitness goals, but as a way to estimate drug dosages and assess surgical risk based on height and sex. Over time, they became widely used reference points for general health discussions. This calculator shows you results from four of the most established formulas side by side so you can see the range rather than treating any single number as a definitive target.
I built this calculator to give you context, not a prescription. These formulas are useful for understanding roughly where your weight sits relative to population averages, but they do not account for muscle mass, bone density, ethnicity, or fitness level — all of which significantly affect what a healthy weight looks like for any individual.
The Four Formulas Compared
Each formula produces a slightly different estimate based on different assumptions about body proportions:
- Hamwi (1964): 48 kg for 152 cm height + 2.7 kg per cm above (men); 45.5 kg + 2.2 kg per cm (women)
- Devine (1974): most widely used in clinical settings; forms the basis of many pharmaceutical dosing guidelines
- Robinson (1983): derived from Metropolitan Life Insurance tables; slightly lower estimates than Devine
- Miller (1983): tends to produce the lowest estimates of the four; may be more appropriate for lighter frames
The spread between the formulas is typically 5–10 kg for the same height. This range itself is informative — it reflects the inherent imprecision of height-based weight estimates.
Why Ideal Weight Is Not the Whole Story
Body composition matters more than body weight. Two people of the same height and weight can have very different health profiles depending on how much of their weight is muscle versus fat. An athlete with high muscle mass may show as "overweight" by these formulas, while someone with low muscle and high body fat may fall exactly in the "ideal" range.
Use this calculator alongside the Body Fat Percentage Calculator and BMI Calculator for a more complete picture. Better still, focus on sustainable habits — strength training, adequate protein, regular movement — rather than chasing a specific number on the scale.
Frequently Asked Questions
Which ideal weight formula is most accurate?
No single formula is universally most accurate — each was developed for a specific purpose and population. The Devine formula is most commonly used in medical settings. For a general health reference, looking at the range across all four formulas gives a more realistic picture than relying on any one result.
Should I try to reach my calculated ideal weight?
Not necessarily. These formulas do not account for muscle mass, age, ethnicity, or activity level. If your current weight is above the range but your body fat percentage and bloodwork are healthy, that is more meaningful than the number a formula produces. Focus on health markers, not just the scale.
Does ideal weight differ by age?
The classic ideal weight formulas do not factor in age. In practice, some research suggests slightly higher weights may be acceptable in older adults, where lower body weight is associated with increased frailty risk. This is an estimate — consult a healthcare provider for personalised weight and health guidance.
