Almost everyone asks: "How much should I weigh?" The answer is not a single number but a range that depends on your height, sex, and body frame. In this article we explain the scientific formulas for calculating ideal weight, why they may differ from BMI, and how to use the result as a realistic goal.
Ideal Body Weight (IBW) is the weight statistically associated with the lowest health risks and best physical performance for a given height. The concept originated in the medical field for calculating drug dosages and then spread to fitness and nutrition.
It is important to understand that it is a range, not a rigid single number. Two people of the same height may have slightly different ideal weights due to differences in bone structure and muscle mass.
Ideal body weight is useful as a directional goal but does not measure health on its own — the distribution of fat and muscle and cardiovascular fitness are equally important factors.
Devine Formula (most commonly used in medicine): For men = 50 kg + 2.3 kg for each inch above 5 feet (152 cm). For women = 45.5 kg + 2.3 kg for each inch above 5 feet.
Example: a man 175 cm tall (≈ 69 inches, meaning 9 inches above 152 cm). Ideal weight = 50 + (2.3 × 9) = 50 + 20.7 ≈ 70.7 kg.
Broca's simplified formula (popular in the Arab world): Ideal weight in kg = Height in cm − 100 for men; Height − 105 for women. Less accurate but quick for a mental estimate.
The most accurate approach is to use the healthy BMI range (18.5–24.9) and convert it to weight: multiply 18.5 and 24.9 by the square of your height in meters to get the lower and upper limits of the healthy range.
Ideal weight formulas (like Devine) give one approximate number, while BMI gives a broader healthy range. Both ignore the ratio of muscle to fat.
Example of a shared limitation: a bodybuilder may exceed the "ideal weight" and be "classified" overweight on both measures, despite having very low body fat. This is why you should not rely on any single number.
Practical advice: use both ideal weight and the healthy BMI range as two guiding indicators, and complement them with waist circumference and body fat percentage for an accurate picture.
Classical formulas (Devine, Broca) rely on height and sex only and do not incorporate age. But in reality, body composition changes with age: muscle mass decreases and the proportion of fat increases at the same weight.
Some studies suggest that a slightly higher healthy weight range may be acceptable for older adults (above 65) as it provides a health reserve during illness. This is an individual medical decision.
More important than chasing a specific number as you age is maintaining muscle mass through resistance training and adequate protein.
Make it a range, not a number: aim to be within a healthy range rather than fixating on a single rigid figure that is difficult to sustain.
Progress safely: do not aim to reach ideal weight rapidly. A sustainable loss of 0.5 kg per week is far better than a harsh temporary diet.
Monitor other indicators: waist circumference measurements, your energy level, sleep quality, and how your clothes fit are sometimes more honest indicators than the number on the scale alone.
A: Ideal weight is an approximate number from a formula (like Devine), while healthy weight is a broader medically acceptable range (usually the range corresponding to BMI between 18.5 and 24.9). Healthy weight is more flexible and realistic as a goal.
A: Yes. People with a larger bone frame (broad bones) may have an ideal weight slightly above the formula's result, and vice versa for those with a small frame. To estimate your frame size, measure your wrist circumference relative to your height.
A: Traditional formulas underestimate athletes with significant muscle. It is better to directly measure body fat percentage (via specialized equipment or tests) rather than relying on ideal weight or BMI.
A: The baseline ideal weight does not change, but returning to it after birth requires time and gradual progress — especially with breastfeeding, which requires additional calories. Consult your doctor before any diet after childbirth.
A: Because each calculator may use a different formula (Devine, Broca, Robinson, or the BMI range). Differences are normal and usually small. Treat the result as an approximate range, not an absolute number.
A: There is no absolute "best" within the healthy range. The most suitable is the weight at which you feel your best energy and performance and can sustain it with a healthy lifestyle, along with healthy body fat and good fitness.