Ideal weight calculator (healthy range)

Ideal weight is not a single figure but a range. At the same height, two healthy people can differ by ten kilograms, depending on muscle mass, frame width and age. That is why the calculator shows you a range first, not a number.

The single figure from the Devine formula appears below it, as a reference point. It is not a target you have to reach.

The range comes from BMI (body mass index), worked backwards. Height in meters is multiplied by itself, and the result is multiplied once by 18.5 and once by 24.9. The two figures are the ends of the World Health Organization's normal weight range [1].

For example, at 1.75 m the range runs from 56.7 kg to 76.4 kg. The upper end is the highest weight at which the displayed BMI is still 24.9. You can check any weight in this range with the body mass index calculator. The range has the same limits as BMI, so it cannot be applied in children, in athletes, in pregnancy or in older people.

The Devine formula was published in 1974, for antibiotic dosing [2]. It starts from 50 kg in men and 45.5 kg in women, for a height of 152 cm, then adds 2.3 kg for every extra 2.54 cm. It is still used today in pharmacology, where the dose of many drugs is based on a theoretical weight rather than on actual body weight.

For a person who wants to know what they should weigh, the formula has serious limits. It takes no account of muscle mass and gives different figures for men and women of the same height. Below 152 cm the formula is extrapolated, and for women up to 145 cm tall the figure falls below the normal weight range [2]. The ideal weight range above remains the most useful reference point.

In a patient with type 2 diabetes, losing 5–10% of current weight improves blood glucose, blood pressure and blood fats [3]. A sustained loss of more than 10% brings greater benefits and can even lead to remission in some patients, especially in the first years after diagnosis [4].

For someone who weighs 100 kg, that means a first target of 90–95 kg, not 75 kg. A target of 5% weight loss is the easiest to reach, and the benefit already begins at that point. A weight target too far from your current weight is discouraging and is often abandoned.