Context : The explosion energy and the ejecta mass of a type IIP supernova make up the basis for the theory of explosion mechanism . So far , these parameters have only been determined for seven events . Aims : Type IIP supernova 2008in is another well-observed event for which a detailed hydrodynamic modeling can be used to derive the supernova parameters . Methods : Hydrodynamic modeling was employed to describe the bolometric light curve and the expansion velocities at the photosphere level . A time-dependent model for hydrogen ionization and excitation was applied to model the H \alpha and H \beta line profiles . Results : We found an ejecta mass of 13.6 \pm 1.9 ~ { } M _ { \sun } , an explosion energy of ( 5.05 \pm 3.4 ) \times 10 ^ { 50 } erg , a presupernova radius of 570 \pm 100 ~ { } R _ { \sun } , and a radioactive ^ { 56 } Ni mass of 0.015 \pm 0.005 ~ { } M _ { \sun } . The estimated progenitor mass is 15.5 \pm 2.2 ~ { } M _ { \sun } . We uncovered a problem of the H \alpha and H \beta description at the early phase , which can not be resolved within a spherically symmetric model . Conclusions : The presupernova of SN 2008in was a normal red supergiant with the minimum mass of the progenitor among eight type IIP supernovae explored by means of the hydrodynamic modeling . The problem of the absence of type IIP supernovae with the progenitor masses < 15 ~ { } M _ { \sun } in this sample remains open .