Why do different ideal weight formulas give different results?

Each formula (Devine, Robinson, Miller, Hamwi) was developed from different reference populations and original purposes, several originally for medication dosing rather than general health guidance, so they don't converge on one universal number.

Do these formulas account for muscle mass or body frame?

No, these formulas are based only on height (and sometimes sex), not body composition, so two people at the same “ideal weight” can have very different amounts of muscle versus fat.

What was the Devine formula originally created for?

It was developed in 1974 primarily for calculating medication dosing, and was later adopted more broadly as a general weight reference despite that original narrower purpose.

Ideal Weight Calculator

Compare ideal weight estimates from four scientific formulas and the healthy BMI range for your height.

Sex

Units

Height — Feet

Height — Inches

Current Weight (optional — for BMI back-calculation)

lbs

About the Formulas

Hamwi (1964) — Originally developed for insulin dosing. Males: 106 lbs for 5 ft + 6 lbs per inch over 5 ft. Females: 100 lbs + 5 lbs/inch.

Devine (1974) — Widely used in pharmacology and ICU settings. Males: 50 kg + 2.3 kg/inch over 5 ft. Females: 45.5 kg + 2.3 kg/inch.

Robinson (1983) — Derived from Metropolitan Life tables. Males: 52 kg + 1.9 kg/inch over 5 ft. Females: 49 kg + 1.7 kg/inch.

Miller (1983) — Another Met Life derivation. Males: 56.2 kg + 1.41 kg/inch over 5 ft. Females: 53.1 kg + 1.36 kg/inch.

How to use

Select your sex and preferred units (Imperial or Metric).
Enter your height.
Optionally enter your current weight to see your current BMI alongside the ideal range.
Click Calculate to see results from all four formulas.
The green healthy BMI range (18.5–24.9) is the most widely accepted guideline.
These formulas were designed for clinical use — use them as a general reference only.

About this Ideal Weight Calculator

There is no single, universally agreed-upon "ideal weight" formula — several different equations exist, developed decades apart for different purposes, and they can produce noticeably different results for the same height.

Common formulas

Devine formula (1974): originally created for medication dosing calculations, later widely adopted as a general reference; 50 kg + 2.3 kg per inch over 5 feet for men (45.5 kg base for women)
Robinson formula (1983): a modification of Devine with adjusted constants
Miller formula (1983): another variation with different base weights and per-inch increments
Hamwi formula (1964): one of the earliest widely used formulas, still referenced in some clinical contexts

Why these formulas disagree

Each formula was developed from different reference populations and for different original purposes (several were created for drug dosing, not general health guidance), which is why they don't converge on a single number. Seeing several results side by side is more informative than treating any one formula as definitive.

What these formulas don't account for

None of these formulas factor in body composition, frame size, muscle mass, or age — two people at the same height and formula-derived "ideal weight" can have very different amounts of muscle versus fat. These numbers work best as a rough reference point, not a personalized target, and are not a substitute for guidance from a healthcare provider.