Contractors in the field can easily calculate board feet with Bear Creek Lumber’s free LumberCalc iPhone application. It takes the known dimensions of lumber, width, length, depth of a board, number of pieces and price per board foot to get the total price and total board feet. It also compares prices with linear feet.
An upcoming paid version of this app includes all the user's feedback such as MBF pricing, fractions of a inch input and also some other lumber specific calculators.
Download it here at the Apple's App store