Ideal Weight Calculator
Estimates your ideal body weight in kilograms using four established clinical formulas — Hamwi, Devine, Robinson, and Miller — based on height and gender. Useful for setting realistic weight-loss or fitness goals.
About this calculator
Four widely cited formulas estimate ideal body weight (IBW) from height in inches above 5 feet (60 inches). Height in cm is converted with: inches = height (cm) / 2.54. The formulas for males and females are: Hamwi — male: 48 + 2.7 × (inches − 60), female: 45.5 + 2.2 × (inches − 60); Devine — male: 50 + 2.3 × (inches − 60), female: 45.5 + 2.3 × (inches − 60); Robinson — male: 52 + 1.9 × (inches − 60), female: 49 + 1.7 × (inches − 60); Miller — male: 56.2 + 1.41 × (inches − 60), female: 53.1 + 1.36 × (inches − 60). These were originally developed to guide medication dosing in clinical settings rather than as aesthetic targets. Results diverge by several kilograms across formulas, so viewing them as a reference range rather than a single number is most useful.
How to use
Suppose a female is 170 cm tall. Step 1 — convert height: 170 / 2.54 = 66.9 inches; inches above 60 = 6.9. Step 2 — Hamwi: 45.5 + 2.2 × 6.9 = 45.5 + 15.2 = 60.7 kg. Step 3 — Devine: 45.5 + 2.3 × 6.9 = 45.5 + 15.9 = 61.4 kg. Step 4 — Robinson: 49 + 1.7 × 6.9 = 49 + 11.7 = 60.7 kg. Step 5 — Miller: 53.1 + 1.36 × 6.9 = 53.1 + 9.4 = 62.5 kg. The four formulas suggest a range of roughly 60.7–62.5 kg for this individual.
Frequently asked questions
What is the most accurate formula for calculating ideal body weight?
No single formula is universally most accurate; each was derived from different populations and for different clinical purposes. The Devine formula is most commonly used in pharmacology for drug dosing. Robinson and Miller were developed as refinements using larger datasets. For general health purposes, the formulas agree closely for average-height individuals but diverge for very short or very tall people. Using the range produced by all four formulas gives a more realistic target than relying on any one method.
How does ideal body weight differ from a healthy BMI weight range?
Ideal body weight formulas produce a single point estimate based only on height and gender, ignoring age, muscle mass, and frame size. A healthy BMI range (18.5–24.9 kg/m²) instead gives a band of acceptable weights and accounts for the same variables. IBW formulas typically fall within or near the lower end of the healthy BMI range. Athletes or heavily muscled individuals may have an actual weight well above the IBW estimate while still being metabolically healthy, which highlights the limitation of both approaches.
Why do the Hamwi, Devine, Robinson, and Miller formulas give different results?
Each formula was derived from a different sample population and era, leading to slightly different intercept and slope values. Hamwi (1964) was designed for diabetes management, Devine (1974) for gentamicin dosing, and Robinson and Miller both appeared in the 1980s as statistical refinements. The differences in the per-inch increments (1.36 to 2.7 kg/inch depending on formula and sex) reflect varying assumptions about bone density and frame size. For most people in the 160–180 cm range the formulas agree within 3–5 kg, which is clinically acceptable.