How the Ideal Weight Calculator works

This calculator uses the Devine formula, published in 1974 by B. J. Devine as a way to estimate body weight for working out medication doses. It later became a common reference point for a healthy weight range. The formula starts from a base weight at a height of 5 feet (152.4 cm) and adds a fixed amount for every inch above that. For men the base is 50 kg, for women it is 45.5 kg, and in both cases 2.3 kg is added per inch (2.54 cm) of height above 5 feet.

The tool then shows a reference range of roughly 10% below to 10% above the calculated figure, because healthy weight is better described as a band than as a single number.

A worked example

Take a man who is 175 cm tall. That is 22.6 cm above 152.4 cm, which is about 8.9 inches. Multiplying 8.9 by 2.3 gives about 20.5 kg, and adding the 50 kg base gives roughly 70.5 kg. The reference range is about 63.4 to 77.5 kg. For a woman who is 165 cm tall, the height above 5 feet is 12.6 cm, or about 5 inches, which adds roughly 11.4 kg to the 45.5 kg base. The result is about 56.9 kg, with a range of about 51.2 to 62.6 kg.

What the result does and does not tell you

The formula uses only height and sex. It cannot see your frame size, muscle mass, bone density, age, or health history, all of which affect what a healthy weight looks like for you. A person with a broad frame or a lot of muscle can be perfectly healthy above the range shown, and someone with a small frame may be comfortable below it. It also was not designed for children, teenagers, or people who are pregnant. For very short heights, the result stays at the base weight, so treat the output with extra care in that case.

Other formulas and why numbers differ

Several other formulas exist, including Hamwi (1964), Robinson (1983), and Miller (1983). Each was built from different data and gives a slightly different figure for the same height, sometimes by several kilograms. None is more correct than the others. They are all rough guides, which is why it helps to compare a few and to look at other measures, such as BMI, waist size, and body fat percentage.

Using the range wisely

Treat the range as a general reference, not a goal you must hit. If you are well above or below it, a doctor or dietitian can help you work out what is realistic and healthy for your body. You can see how your current weight compares using the BMI Calculator, and get a better sense of your body composition with the Body Fat % Calculator. This tool gives general information only and is not medical advice.

It also helps to think in trends rather than single readings. Body weight naturally moves by a kilogram or two from day to day with water, food, and hormones, so comparing a weekly average is more meaningful than comparing one morning to the next. If your weight has been stable for years and you feel well, that is usually more informative than any formula.