Using this app you can calculate your Body Mass Index(BMI) also you calculate Body Fat Percentage(BFP) just on One Click.

Who shouldn't use a BMI calculator :
BMI is not used for muscle builders, long distance athletes, pregnant women, the elderly or young children. This is because BMI does not take into account whether the weight is carried as muscle or fat, just the number. Those with a higher muscle mass, such as athletes, may have a high BMI but not be at greater health risk. Those with a lower muscle mass, such as children who have not completed their growth or the elderly who may be losing some muscle mass may have a lower BMI. During pregnancy and lactation, a woman's body composition changes, so using BMI is not appropriate.

Note : For persons 65 years and older the 'normal' range may begin slightly above BMI 18.5 and extend into the 'overweight' range.

Source: Health Canada. Canadian Guidelines for Body Weight Classification in Adults. Harvard Medical School.

Ottawa: Minister of Public Works and Government Services Canada

The American Council on Exercise Body Fat Categorization.