On this site, you can calculate your body mass index (BMI). Enter your weight in kilograms, your body size in centimeters and click Calculate. Seem also BMI for children.
The body mass index is the ratio of weight to height squared. Weight is relatively easy to determine and height does not change in adults, so the BMI is often used. The higher the weight and the lower the height, the higher the BMI. A high body mass index is therefore associated with being overweight. The BMI does not say what the body is made of, i.e. whether the possible excess weight is due to fat deposits or muscle mass. This is a shortcoming of this measurement. The ABSI and thewaist to hip ratio are more meaningful in terms of health risks, but they are a little more difficult to determine. Nevertheless, the BMI is also justified, as you can roughly estimate yourself how muscular you are. Ideally, you determine all three values and have them interpreted by experts. Bone density is not taken into account by any of these measurement methods, and there can be differences here too, but this is generally measured using X-rays and is therefore reserved for the according facilities.
There is statistical evidence that mortality is lowest with a BMI between 20 and 25, meaning that these people tend to live to a higher age as those with higher or lower values. It is probably safe to assume that extreme BMI values are detrimental to health.