Optimal weight for your height can be calculated using body mass index (BMI) calculators online. Or you can calculate it yourself: the formula of BMI is kg of the body weight divided into m2, where kg is a person's weight in kilograms and m2 is their height in meters squared. The perfect range of BMI is between 18.5 and 24.9. If your BMI turns out to be higher than that, you can calculate the optimal weight trying different weight numbers in the formula.