Ideal Weight Calculator

Only your sex and height are needed, so the result appears as soon as the fields are filled.

1. Choose your Sex, Male or Female. Each formula has a separate starting weight and rate for the two.
2. Set Units to Metric (cm, kg) or Imperial (ft/in, lb). This also decides whether weights are shown in kilograms or pounds.
3. On metric, type your Height (cm). On imperial, fill in Height: feet and Height: inches instead.
4. Read the large figure at the top, which is the average of the four formulas, together with the healthy BMI range for your height.
5. Scroll through the rows to compare Devine, Robinson, Miller and Hamwi, and check the height the tool actually used.

Imperial users should enter inches as a number below 12, for instance 5 feet and 9 inches rather than 5 feet and 21 inches. The tool converts to centimetres internally, and the Height used row shows the figure it worked from, so you can confirm that nothing was mistyped.

All four formulas are linear. They start from a base weight for a person exactly 5 ft (60 inches) tall and add a fixed number of kilograms for each inch above that. Let n be the inches over 60:

Take a man who is 175 cm tall, which is 5 ft 8.9 in, so n is about 8.9. Devine gives 70.5 kg, Robinson 68.9 kg, Miller 68.7 kg and Hamwi 72.0 kg. The average is 70.0 kg, and the spread between the lowest and highest formula is only 3.3 kg. For a woman who is 165 cm tall (n is about 5.0) the same method gives roughly 56.9, 57.4, 59.8 and 56.4 kg, an average near 57.7 kg.

The formulas have different histories. Devine was first written to help with medication dosing, Hamwi was a rule of thumb used in clinical nutrition, and Robinson and Miller were 1983 revisions that tried to fit measured data better. None of them was designed to say what you should weigh.

Because the lines are straight, each extra inch of height adds the same amount, between about 1.4 and 2.7 kg depending on the formula and sex. That is why Hamwi, with the steepest slope for men, gives the highest figure in the example and why the four results drift further apart for very tall people.

The tool always shows a second line: the weights that give a BMI between 18.5 and 24.9 at your height. For the 175 cm example that is 56.7 to 76.3 kg, a window of almost 20 kg, and every one of the four formula results sits inside it. For the 165 cm example it runs from 50.4 to 67.8 kg. A single ideal weight suggests a precision that does not exist, while a range reflects how much healthy bodies vary. If you want the BMI itself for a particular weight, use the BMI calculator.

Know the limits before you act on any number here. The formulas date from the 1960s to the 1980s and ignore frame size, muscle mass, age and ethnicity. They were designed for adults above 5 ft (152 cm), and below that height the tool displays a warning, because the results are extrapolated and the BMI range becomes the safer reference. A muscular athlete can sit above the range and be perfectly healthy, and body composition says more than scale weight, which is where the body fat calculator helps.

The output is an estimate for general information and is not medical advice. If you are thinking about changing your weight, a doctor or dietitian can take your whole situation into account. To see how energy intake fits into that, the calorie calculator is a sensible next stop, and the weight converter switches between kilograms, pounds and stones. When you compare the result with your own weight, use the same scale, at the same time of day, because weight can vary by a kilogram or two within a single day.