There are few things that make people feel vaguely inadequate as efficiently as being told their "ideal weight". Type your height into an ideal weight calculator and out comes a number — sometimes with a reassuringly scientific-looking formula name attached. But how reliable are these numbers? Who invented them, and for what purpose? As it turns out, the history of ideal weight formulas is rather more interesting — and rather less rigorous — than you'd expect.
Where Did Ideal Weight Formulas Come From?
The most widely used ideal body weight (IBW) formulas were actually developed in the 1960s by Dr B.J. Devine — not for general health, but to calculate drug dosages for patients. The formula was designed to estimate lean body mass for pharmacological purposes, not to define what any given individual should weigh to be healthy.
The Devine formula (still used in many calculators today) gives: for men, 50kg + 2.3kg per inch above 5 feet; for women, 45.5kg + 2.3kg per inch above 5 feet. Our ideal weight calculator uses multiple formulas so you can compare across approaches.
The Robinson, Miller and Hamwi Formulas
Several other formulas exist, developed around the same era:
- Robinson (1983): 52kg + 1.9kg per inch over 5' (men); 49kg + 1.7kg per inch over 5' (women)
- Miller (1983): 56.2kg + 1.41kg per inch over 5' (men); 53.1kg + 1.36kg per inch over 5' (women)
- Hamwi (1964): 48kg + 2.7kg per inch over 5' (men); 45.5kg + 2.2kg per inch over 5' (women)
These formulas produce different numbers for the same person. A 5'10" man gets "ideal weights" ranging from roughly 71-79kg depending on which formula you use. The variation itself suggests these are rough guides, not precise targets.
What These Formulas Don't Account For
The fundamental limitation of all height-based ideal weight formulas is that they ignore body composition entirely — the same problem as BMI. A muscular athlete might be well above their "ideal weight" while having excellent health metrics. An older individual might hit their "ideal weight" number while having low muscle mass and metabolically unhealthy fat distribution.
They also don't account for age, sex differences in muscle mass, frame size, or ethnicity. The formulas were developed primarily on white European populations, and may not translate accurately across all ethnicities.
Pair any ideal weight figure with our BMI calculator and a waist measurement for a more rounded picture.
Healthy Weight Range vs Ideal Weight
Rather than a specific ideal weight, most current health guidance points to a healthy weight range. The BMI-based healthy range (18.5-24.9) translates to a range of approximately 7-10kg for most heights — recognising that there is no single ideal weight for a given height.
For a 5'8" (172cm) person, the healthy BMI range translates to roughly 55-73kg. That's an 18kg range — suggesting that many different weights can be entirely healthy for the same height, depending on the individual.
A More Useful Approach
Instead of targeting a specific "ideal weight", consider tracking:
- Body fat percentage — a direct measure of body composition
- Waist circumference — a proxy for visceral fat risk
- Functional fitness — can you do the physical things you want to do?
- Health markers — blood pressure, blood glucose, cholesterol, resting heart rate
So Should You Use an Ideal Weight Calculator?
As a rough orientation tool, yes — with clear-eyed awareness of its limitations. It can help you understand broadly whether your current weight is in a reasonable zone for your height, and give you a starting goal if you're unsure where to aim.
But don't treat the output as a target carved in stone. Your body is not an average. Health is measured by how you feel, how your body functions, and what your blood tests show — not by whether you match a 1960s drug-dosing formula.
Further reading: The NHS has straightforward, practical guidance on healthy weight for adults. Visit the NHS healthy weight guidance.