Perfect Weight Calculator — Your Ideal Body Weight by Height

Work out your ideal body weight from your height, sex and frame size. This free calculator runs the four formulas clinicians and dietitians still use — Robinson, Miller, Devine and Hamwi — and shows the healthy weight range for your height alongside them, so you get a realistic band rather than one number. Heights in cm or feet and inches, results in kg or pounds.

How to Work Out Your Ideal Weight

  1. Enter your height in centimetres, or in feet and inches.
  2. Choose your sex and frame size (small, medium or large). Frame matters: the same height carries more weight on a wider skeleton.
  3. Read the range, not a single figure. The four formulas rarely agree exactly, and the spread between them is the honest answer.

The Four Formulas, and Why They Differ

FormulaYearKnown for
Robinson1983A refinement of Devine; usually the lowest of the four
Miller1983Gentler on taller people than Robinson
Devine1974Written for medicine dosing, now the most quoted
Hamwi1964The oldest, and the most generous at greater heights

They were all built on population averages, not on you. Treat the spread as a target zone.

Ideal Weight and BMI Are Not the Same Thing

The calculator also shows the weight range that puts your BMI between 18.5 and 24.9, the range the WHO calls healthy. BMI takes no account of muscle, bone or frame, which is why a muscular athlete can read “overweight” while sitting at a low body-fat percentage. Where the formulas and the BMI range overlap is the most defensible target.

Frequently Asked Questions

What is my ideal weight for my height?
Enter your height, sex and frame size above. You will get four formula results plus the healthy BMI range for your height — usually a band of several kilograms rather than a single figure.
Why do the four formulas give different answers?
They were derived from different populations between 1964 and 1983. Hamwi tends to be the most generous at greater heights and Robinson the strictest; the gap between them widens the taller you are.
Does body frame really change ideal weight?
Yes. Bone width and joint size vary between people of the same height, so the calculator adjusts the result for a small, medium or large frame.
Is ideal body weight the same as a healthy weight?
No. Ideal body weight is a formula estimate; a healthy weight is a range that also depends on muscle mass, body composition, age and health history. Use the result as a guide and talk to a doctor or dietitian before setting a target.