First, let me clarify - you're asking about body fat - not Body
Mass Index. BMI is helpful in estimating whether you're overweight
or not, and can be checked with a calculat…or online - but does not
give you any real indication of body fat percentage.
For that, you'll need a Body Fat Caliper tool. There are more
accurate methods of determining body fat percentage, but this is
the best solution if you're on a budget. Calipers are simple to
use, fairly accurate, and don't hurt (MORE)