NUM * 11101.01 binary
is
NUM * 29.25 decimal
which
will give you an answer within 0.5% of your desired result and allow you to use a simple byte multiply. If you have a 9bit number to multiply, it takes a small step to do it likewise.

Remember this, if you sensor is not well calibrated and accurate, computing a highly precise algorithm is a waste of brainpower and time.