Ideal Weight Calculator
Compare ideal body weight for your height from the Hamwi, Devine, Robinson and Miller formulas, with their average in pounds and kilograms.
Note: Ideal weight formulas provide general estimates based on height and gender. They do not account for body composition, muscle mass, or individual health factors. Consult a healthcare professional for personalized guidance.
Updated Formula covered by automated tests
Ideal body weight formulas turn a single input, your height, into a reference weight. This calculator runs the four best-known versions (Hamwi, Devine, Robinson and Miller) side by side and averages them, so you can see how much the answer depends on which formula you pick. Results are shown in pounds and kilograms for heights from 5 ft upward.
Despite the name, these numbers were never meant as personal goals. Their main professional use today is in hospitals and pharmacies, where dosing for some drugs, ventilator settings and kidney function estimates are based on an ideal or predicted body weight rather than actual weight. Many people also use them as a sanity check next to a BMI-based healthy range.
The formula
- inches over 5 ft
- Your height in inches minus 60; metric heights are divided by 2.54 first, so 170 cm is 66.93 in, or 6.93 in over
- base weight
- The reference weight each author assigned to someone exactly 5 ft (152.4 cm) tall
- per-inch increment
- How much weight the formula adds for every extra inch of height
- average
- Simple mean of the four results, shown to smooth out the differences between authors
G. J. Hamwi published the oldest rule in 1964 as a quick bedside estimate for diabetes meal planning. Ben Devine proposed his version in 1974 to help calculate doses of the antibiotic gentamicin, and it became the default in pharmacy almost by accident. In 1983 two teams, J. D. Robinson and colleagues and D. R. Miller and colleagues, refitted the idea to Metropolitan Life insurance height-weight tables, producing formulas with smaller increments per inch.
All four share the same structure: a straight line that starts at 5 ft and climbs a fixed amount per inch. That is why they agree fairly well near average height and drift apart for very tall people. Because they ignore age, frame size and body composition, clinicians treat the output as a reference value rather than a target.
Worked example
Hannah is 5 ft 6 in tall (66 in, or 167.6 cm) and wants to see what the classic formulas say for a woman of her height.
- 1 Inches over 5 ft: 66 − 60 = 6.
- 2 Devine: 45.5 + 2.3 × 6 = 59.3 kg. Robinson: 49 + 1.7 × 6 = 59.2 kg.
- 3 Miller: 53.1 + 1.36 × 6 = 61.26 kg.
- 4 Hamwi: 100 + 5 × 6 = 130 lb, and 130 × 0.45359237 = 58.97 kg.
- 5 Average: (58.97 + 59.3 + 59.2 + 61.26) ÷ 4 = 59.68 kg, about 131.6 lb.
Result: The four formulas put Hannah between about 59.0 and 61.3 kg (130 to 135 lb), with an average of 59.7 kg. For comparison, a BMI of 18.5 to 24.9 at her height spans roughly 52 to 70 kg, a much wider band.
Before you rely on the result
- The formulas take no account of age, muscle mass, bone structure or ethnicity, and they were derived mainly from data on white American adults.
- They are not intended for children, teenagers, pregnant women or people under 5 ft tall.
- If you need a weight figure for a medical decision, such as a medication dose, rely on the value your care team calculates rather than this page.
Frequently asked questions
Why do the four formulas give different answers?
They were built for different purposes from different data. Hamwi and Devine were quick clinical rules, while Robinson and Miller were fitted to insurance-company tables. The per-inch increments range from 1.36 to 2.3 kg, so the gap widens as height increases.
Should I diet until I reach my ideal body weight?
Not necessarily. The formulas give one number for everyone of a given height and sex, but healthy people of the same height can differ by 15 kg or more depending on frame and muscle. A doctor or registered dietitian can help you decide whether a change in weight would benefit your health.
Why does the calculator refuse heights under 5 feet?
Every formula is defined as a base value at 5 ft plus an amount per inch above it. The original papers did not specify how to handle shorter adults, and the ad hoc fixes found online (such as subtracting a set amount per inch) are not standardized, so the calculator does not guess.
Is ideal body weight the same as a healthy BMI weight?
No. The BMI method gives a range, from a BMI of 18.5 to 24.9, while these formulas give a single point that usually falls in the lower half of that range. Hospitals sometimes use both: ideal weight for drug doses and BMI for screening.