Ideal Weight Reference
Two formulas, their disagreement, and what none of them can see. Read the last section first.
BFCBrilliance · bfcbrilliance.com/tools/ideal-weight-calculator
The formulas
- Structure of all of them
- a base at 5 ft + a fixed amount per inch above
- Devine (1974), men
- 50 kg + 2.3 kg per inch over 5 ft
- Devine, women
- 45.5 kg + 2.3 kg per inch
- Hamwi (1964), men
- 106 lb + 6 lb per inch
- Hamwi, women
- 100 lb + 5 lb per inch
- Also in use
- Robinson · Miller — in and around the same spread
- ⚠ They disagree by
- 1.3 lb at 5'6" · 5.1 at 5'10" · 12.5 at 6'6" (men)
- ⚠ Built for
- DOSING MEDICATION, not personal targets
- ⚠ Least reliable for
- very tall, very short, very lean people
What none of them can see
- Body composition
- invisible — muscle and fat weigh the same
- Frame size
- invisible
- Age
- invisible
- Ethnicity
- invisible
- Pregnancy
- invisible
- Your actual health
- invisible
- The only input is
- HEIGHT
They were built to dose drugs
Developed so clinicians could estimate lean body mass quickly at the bedside, because some medications are dosed on lean mass rather than actual weight. Never designed as a personal target — which explains why they use height alone, and why nobody involved cared whether the answer felt motivating.
The disagreement is the finding
Several formulas built for the same job by serious people disagree — and disagree MORE the further you get from average height. For men the two here are 1.3 lb apart at 5'6" and 12.5 lb apart at 6'6". That gap is not noise around a true value; it is evidence that no height-only formula knows a precise fact about your body. Any calculator showing one confident number is hiding this.