There are a variety of ways in which to assess one's body fat and weight, and the most accurate way of doing so is a consultation with a GP or physician. A medical professional is able to assess the height and weight, as well as muscle tone and bone density - both of which may have a disproportionate effect on the weight, and which may suggest a weight problem which does not exist.
A useful indicator of body fat, however, is the body mass index (BMI). This assessment is based on the height and weight, and gives an indication of healthy proportions for an individual's height. The scale is commonly used by medical professionals and individual's to give an accurate estimate of body fat, but is not appropriate for individual's under the age of 18 or over the age of 65.
An average BMI will be between 20 and 25, and this indicates that the individual is of a normal, healthy weight. Those with a score below 20 may be underweight, and those with a score of more than 25 may be overweight. Where the score is higher than 30, this suggests that the individual is obese.
The formula for calculating the body mass index is [height] / [weight]². Height and weight can be entered in either imperial or metric measurements, but both must be given in the same form to ensure an accurate calculation.