Ideal Body Weight
Ideal body weight is a weight estimated from height and sex using formulas such as Devine, Robinson, Miller or Hamwi. They were built for clinical purposes like drug dosing, not for fitness goals, and they cannot see frame size or muscle mass.
Ideal Body Weight: what is it?
Clients ask what they should weigh, and there is a whole family of formulas that answer confidently. It is worth knowing where those formulas came from, because it explains why they feel so blunt. Most were developed to standardise clinical decisions, drug dosing above all, where a rough height-based reference is far better than nothing and precision was never the point. None of them were designed to give a lifter a target. They take height and sex, and that is all, which means two clients of identical height get the same answer regardless of frame, muscle mass or training history.
The main formulas and how they differ
The formulas below are all built the same way: a base weight at 5 feet, plus a fixed increment per additional inch. They disagree with each other by several kilograms at the same height, which is the clearest possible evidence that no single "ideal" weight exists.
| Formula | Men | Women |
|---|---|---|
| Devine | 50 kg + 2.3 kg per inch over 5 ft | 45.5 kg + 2.3 kg per inch over 5 ft |
| Robinson | 52 kg + 1.9 kg per inch over 5 ft | 49 kg + 1.7 kg per inch over 5 ft |
| Miller | 56.2 kg + 1.41 kg per inch over 5 ft | 53.1 kg + 1.36 kg per inch over 5 ft |
| Hamwi | 48 kg + 2.7 kg per inch over 5 ft | 45.5 kg + 2.2 kg per inch over 5 ft |
What the formulas can't see
Height and sex are the only inputs. That means frame size is invisible: a client with wide shoulders and thick wrists gets the same answer as a small-framed client of the same height, and one of those two answers will be badly wrong. Muscle mass is invisible for the same reason, which is why a trained lifter routinely sits well above every one of these formulas while carrying low body fat.
Age, ethnicity and body composition are all absent too. Handed to a client without that context, an ideal body weight figure produces one of two bad outcomes: a lean muscular client who thinks they need to lose weight, or a client with very little muscle who thinks they are already where they should be.
A more useful alternative: a healthy weight range
Rather than a single number, the healthy BMI band converted back into kilograms gives a range, which is both more honest and more usable. Multiply 18.5 and 24.9 by height in metres squared and you get the two ends. For a client at 1.75 m that is roughly 56.7 kg to 76.3 kg, a spread of nearly twenty kilograms, which is exactly the point: within that band, body composition decides everything.
Layer waist circumference on top and you have something genuinely informative. A client at the upper end of the range with a waist under the screening thresholds is in a different situation from a client at the same weight with a waist above them, and no ideal weight formula can tell those two apart.
How to use it with a client anyway
The formulas still have one legitimate coaching use: as a conversational anchor. When a client says they want to weigh 55 kg at 1.78 m, showing them that every standard formula and the healthy BMI range put them well above that is a calm, external way of opening a conversation you would otherwise have to make personal.
Never set it as a goal. Goals belong on things the client controls and that reflect what they actually want, which is usually waist measurement, strength markers, how clothes fit, and progress photos. Ideal body weight is a reference point on a chart, not a destination.
Key takeaways
- Devine, Robinson, Miller and Hamwi all take only height and sex, and they disagree with each other.
- They were built for clinical uses such as drug dosing, not for fitness or aesthetic goals.
- They are blind to frame size, muscle mass, age and body composition.
- A healthy weight range from the BMI band, read next to waist circumference, is more useful than any single number.
- Use it to anchor a conversation, never as a client target.
Frequently asked questions
Which ideal body weight formula is the most accurate?
None of them, in the sense clients mean. They disagree with each other by several kilograms at the same height because they were fitted to different reference data for different clinical purposes. Devine is the most widely used in practice, largely for historical reasons in drug dosing, not because it describes an individual better.
Why does the formula say my athlete is overweight?
Because it only knows their height and sex. A trained athlete carries substantially more lean tissue than the reference populations these formulas were built on, so they sit above the calculated weight while being lean. This is the same failure mode as BMI, and the fix is the same: look at body fat, waist circumference and photos instead.
Should I give a client an ideal body weight target?
No. Give them a healthy range and then coach the things the range cannot see: waist circumference, strength markers, progress photos and how clothes fit. A single scale target sets clients up to chase a number that may be wrong for their build and takes no account of the muscle they are about to gain.
Updated August 28, 2026
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