Ideal Weight: What the Formulas Do — and Don't — Tell You
Health · 6 min read · Last updated September 2026
The Devine formula (the classic single number)
Women: 45.5 kg + 2.3 kg per inch over 5 ft
Built in 1974 to dose medication, not to set fitness goals. Example: a 5′10″ (70-inch) man: 50 + 2.3 × 10 = 73.0 kg; a 5′10″ woman: 45.5 + 23 = 68.5 kg. It ignores muscle, age and frame entirely — that is a feature for drug dosing and a limitation for everything else.
The healthy-BMI range (a range, honestly)
At 1.75 m: 18.5 × 3.0625 = 56.7 kg up to 24.9 × 3.0625 = 76.3 kg — a 20-kilogram-wide band. The BMI range is broader than Devine precisely because bodies vary more than a dosing formula can express.
Why the two disagree — and which to use
| Method | 5′10″ male | Answers the question |
|---|---|---|
| Devine | 73.0 kg | "What does a population-average body of this height weigh?" |
| Healthy BMI | 56.7–76.3 kg | "What range is statistically associated with lower health risk?" |
Use the range for context, not a target to hit exactly. A muscular 78 kg person at 1.75 m sits above the BMI band but is not unhealthy; a sedentary 70 kg person inside it may carry more risk than the number suggests. Pair the result with the BMI Calculator and — more informatively — a waist measurement or body-fat estimate.
Try the calculators
Worked example: Ideal Body Weight at its default inputs
Take the default setup on Ideal Body Weight: no fields changed, nothing tuned to a nice round number. Run in the site's own engine, those values produce the answer below.
| Input | Default |
|---|---|
| Height (cm) | 175 |
Result: ~70.5 kg
The steps behind that answer
- Height in inches: 68.9
- Hamwi: 72.0 kg | Devine: 70.5 kg
- Robinson: 68.9 kg | Average ≈ 70.5 kg
Sensitivity: Height (cm) from half to one-and-a-half times
Same calculator, same fields, one change: height (cm).
| Height (cm) | Result |
|---|---|
| 87.5 | ~-8.8 kg |
| 175 | ~70.5 kg |
| 262.5 | ~149.7 kg |
Halve height (cm) and the result moves one way; add half again and it moves the other. Watching that gap is quicker than guessing which field matters most.
Related guides
Formulas describe populations, not people
Ideal-weight formulas were built from insurance and military data to describe average healthy weights for heights. They were never designed to tell an individual what to weigh, and they disagree with each other by several kilograms for the same height.
Treat the output as a reference band. Body composition, frame size, age and training history all sit outside the formula, and none of them are wrong for being outside it.
BMI and ideal weight measure different things
BMI relates weight to height squared and says nothing about muscle or fat distribution. Ideal-weight formulas usually add a frame adjustment. Someone with substantial muscle can be over an ideal-weight figure and metabolically healthy; someone with low muscle can be inside it and not.
Waist measurement and body-fat percentage add information that height-and-weight numbers cannot. Use them together rather than choosing the easiest one.
Targets for real goals
For health outcomes, a 5-10% reduction from current weight already improves blood pressure and glucose control in most people with excess weight. Aiming directly at a formula number skips the part with the best evidence.
For performance, the target is a body composition and a rate of change, not a scale weight. Losing more than about 1% of body weight a week usually costs muscle.
Frequently asked questions
What is the ideal weight for my height?
There is no single number. The healthy-BMI range for your height (18.5–24.9 × height in meters squared) is the most defensible reference band — for 1.75 m that is about 56.7–76.3 kg — and formulas like Devine give a narrower population average inside or near it.
How do I calculate ideal weight by hand?
Devine: men, 50 kg + 2.3 kg per inch over 5 feet; women, 45.5 kg + 2.3 kg per inch over 5 feet. For the BMI range, multiply your height in meters by itself, then by 18.5 and by 24.9.
Is ideal weight the same as healthy weight?
Not exactly. Ideal-weight formulas give one point estimate from height alone; healthy weight is better expressed as the BMI-associated range, which is wider because muscle, frame and body composition vary.
Why does the calculator show a range instead of one number?
Because a range is the honest output. Bodies at the same height legitimately differ by 15–20 kg while remaining healthy; a single kilogram figure implies precision the underlying data does not support.
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