Ideal Weight Range Calculator
Estimate your healthy weight range using the Hamwi formula adjusted for frame size, age, and sex. Use it to set a realistic goal weight before starting a diet or fitness program.
About this calculator
Ideal body weight formulas provide a personalized target range rather than a single number. This calculator uses the Hamwi method as its base: for males, IBW = 106 lbs + 6 lbs per inch over 5 feet; for females, IBW = 100 lbs + 5 lbs per inch over 5 feet. Frame size then adjusts the result: small frames subtract 10% and large frames add 10%. An age adjustment adds weight for adults over 25 — 0.5 lbs/year for males and 0.3 lbs/year for females — reflecting that body composition naturally shifts with age. The full formula is: IBW = (base + heightAdjustment) × frameFactor + ageAdjustment. These methods give a practical target range rather than the overly rigid single values produced by simple BMI lookups.
How to use
Example: a 35-year-old male, 70 inches tall (5'10"), medium frame. Step 1: Base = 106 lbs. Step 2: Inches over 60 = 10; add 10 × 6 = 60 lbs → 166 lbs. Step 3: Medium frame multiplier = 1.0 → 166 × 1.0 = 166 lbs. Step 4: Age over 25 = 10 years; add 10 × 0.5 = 5 lbs. Step 5: Ideal weight = 166 + 5 = 171 lbs. A small frame would give 166 × 0.9 + 5 = 154 lbs, and a large frame 166 × 1.1 + 5 = 188 lbs.
Frequently asked questions
What is the Hamwi formula and why is it used to calculate ideal body weight?
The Hamwi formula was developed in 1964 by Dr. G.J. Hamwi as a quick clinical tool for estimating ideal body weight in patients. It bases the calculation on height relative to a 5-foot baseline and adds a fixed increment per additional inch. It remains widely used because it is simple, transparent, and correlates reasonably well with metabolic health outcomes. Unlike BMI alone, it can be adjusted for frame size, making it more individualized for clinical and personal use.
How does frame size affect my ideal weight and how do I determine my frame size?
Frame size accounts for the weight of your skeletal structure, which varies significantly between individuals. A person with a larger bone structure will naturally weigh more at the same height without carrying excess fat. You can estimate frame size by wrapping your thumb and middle finger around your wrist: if they overlap you are small-framed, if they touch you are medium, and if they do not meet you are large-framed. This calculator applies a 10% reduction for small frames and a 10% increase for large frames on the base ideal weight.
Should I use ideal weight or BMI to set my weight loss goal?
Both metrics have limitations when used alone. BMI does not distinguish between fat and muscle, and it ignores frame size, making it misleading for athletic or broad-framed individuals. Ideal weight formulas like Hamwi and Robinson are more personalized but still do not account for body composition directly. The most useful approach is to use ideal weight as a rough target range and then refine it with body fat percentage measurements as you progress. A goal weight that puts you in a healthy body fat range is more meaningful than any formula-derived number alone.