A standard weight of between 55.1 kilograms and 66.1 kilograms is normal for a girl of 166cm. In the absence of the pursuit of extreme thinness, a healthy height and weight as a standard, you can take the internationally recognized body mass index formula for assessment. That is, the BMI index, the normal BMI index is between 20 and 24. The specific formula is weight (kg) divided by the square of height (meters). If you know the height, you can also invert the number of healthy standard weight. This value can be used as a reference for whether the body type is too thin or too fat. When the actual weight is less than 55.1 kilograms too much, it is necessary to consider whether there is malnutrition. When the actual weight is greater than 66.1 kg more, it suggests the possibility of obesity. It is important to note that this is only a reference standard, and if there are no problems with physical fitness or other body functions, it is generally fine to be a little out of the range. If the weight deviation is too large, accompanied by physical discomfort, then you should immediately consult a doctor for examination and treatment.