A dry powder inhaler dispenses a partial dosage of a powder from a dry powder chamber during a single user inhalation. In certain embodiments, the dry powder chamber is a dry powder capsule that spins in a chamber with a protrusion for limiting the spin of the capsule. In certain embodiments, a capsule slides in a proximal and distal direction for dispensing partial dosages of powder medicament. Air inlets in communication whit the external environment can be included in the inhaler housing for generating a smooth inhalation experience for the user and facilitating operation of partial dosage mechanisms. In other embodiments, a hinged member, sliding member, rotating member, spring tensioned member, pressure actuated valve, dry powder chamber with patterned holes or combinations of these are used as a mechanism for dispensing a partial dosage of powder medicament during a single inhalation.