How the ideal weight calculator works
The calculator shows you three values side by side, because there is no single scientifically defined ideal weight:
- Broca formula: normal weight = height (cm) − 100. For the ideal weight, men subtract 10 percent from that, women 15 percent. Example at 175 cm: normal weight 75 kg, ideal weight 67.5 kg (man) or 63.75 kg (woman).
- Devine formula (1974): men 50 kg, women 45.5 kg, in each case plus 2.3 kg per inch above 152.4 cm (5 feet). In metric terms, that is roughly 0.9 kg per centimeter above 152.4 cm (rounded, the exact figure is 2.3 kg per 2.54 cm).
- Healthy weight range (WHO): all weights corresponding to a BMI of 18.5 to 24.9, that is from 18.5 × height (m)² to 24.9 × height (m)². At 175 cm, that is roughly 56.7 to 76.3 kg.
Here is how the three approaches compare directly at a height of 175 cm:
| Formula | Man (175 cm) | Woman (175 cm) |
|---|---|---|
| Broca normal weight | 75.0 kg | 75.0 kg |
| Broca ideal weight | 67.5 kg | 63.8 kg |
| Devine formula (1974) | 70.5 kg | 66.0 kg |
| Healthy WHO range | 56.7 to 76.3 kg | 56.7 to 76.3 kg |
Notably, Broca and Devine produce different single numbers, but both fall within the WHO range. That makes the range the most reliable of the three points of reference.
Healthy weight range by height (WHO)
The World Health Organization classifies a BMI of 18.5 to 24.9 as normal weight in adults. From that, this range follows for each height:
| Height | Healthy range (BMI 18.5 to 24.9) |
|---|---|
| 155 cm | 44.4 to 59.8 kg |
| 160 cm | 47.4 to 63.7 kg |
| 165 cm | 50.4 to 67.8 kg |
| 170 cm | 53.5 to 72.0 kg |
| 175 cm | 56.7 to 76.3 kg |
| 180 cm | 59.9 to 80.7 kg |
| 185 cm | 63.3 to 85.2 kg |
| 190 cm | 66.8 to 89.9 kg |
| 195 cm | 70.3 to 94.7 kg |
Where the Broca and Devine formulas come from
The Broca formula goes back to the French surgeon and anthropologist Pierre Paul Broca (1824 to 1880) and dates from the 19th century. It was never intended as a precision instrument and only roughly applies to heights between about 160 and 180 cm. A side note for formula collectors: some historical accounts mention a deduction of 20 percent for women, but the variant with 15 percent is the one that prevailed.
The Devine formula was published by B. J. Devine in 1974 in a journal article on gentamicin therapy. Originally it was not a general ideal weight at all, but a reference value for tying the dosage of certain antibiotics (aminoglycosides such as gentamicin) to body height. Pai and Paloucek showed in 2000 that the formula was based on empirical estimates, not on a referenced population study. The fact that it appears in many ideal weight calculators today is more of a historical accident than a scientific seal of approval.
Why a single number says very little
All ideal weight formulas share the same blind spots:
- Muscle or fat: neither Broca nor Devine nor the BMI distinguish between muscle and fat mass. The same number can stand for very different body compositions.
- Misclassification is measurable: a DXA-based study from Northern Italy (ages 18 to 98) found that the BMI categories misclassify 32.5 percent of adults overall compared with their measured body fat percentage. In the normal weight category, 21.9 percent were misclassified, in the overweight category as much as 53.4 percent.
- Age: as we get older, body fat increases (including belly fat) while muscle mass declines, often at a stable weight. A fixed ideal number does not capture that.
- Body build: Broca and Devine completely ignore bone structure and frame. For very short, very tall and muscular people, the formulas are of no use.
A healthy weight range is therefore a better guide than a fixed ideal number, complemented by waist circumference or the waist-to-hip ratio. You will find the quick waist-to-height check right in our BMI calculator.
From target weight to everyday life: next steps
Once you know where you want to go, the next step is a look at your energy intake: the calorie calculator shows you how many calories your body needs each day. You will find clear, myth-free knowledge in our nutrition basics, and ideas for cooking in our healthy recipes. And if you want to change your weight for good, a qualified nutrition coach near you or online can help you with a plan that fits your life.