A quick and somewhat dirty way to calculate an inductor value for buck regulators operating in constant conduction mode (CCM). http://electronics.stackexchange.com/questions/49280/how-to-choose-a-inductor-for-a-buck-regulator-circuit    

Inductance Inductance “rolls off” with increasing current and the way this happens depends on the material: Iron powder, molybdenum permalloy powder (MPP), sendust and amorphous powder that employ a distributed air gap Inductance roll off starts at very low current levels and continues in an almost linear manner as the current is increased. The peak […]