Reliable　predictions　of　electronic　levels,　excited-state　geometric　relaxation,　and　the　relative　energies　of　ground　and　excited　levels　to　host　band　edges　are　of　paramount　importance　for　Ce3+-doped　luminescent　materials.　By　combining　the　constrained　occupancy　approach　and　the　hybrid　density　functional　calculation　in　the　framework　of　a　generalized　Kohn-Sham　formalism,　we　derived　a　calculation　scheme　for　the　band　gap　of　the　host　material,　the　equilibrium　configurations　of　ground-state　Ce3+　and　excited-state　(Ce3+)*,　and　their　relative　energies　with　respect　to　host　band　edges　in　terms　of　hole　capture　or　electron　ionization　for　Ce3+　in　M2B5O9Cl　(M　=　Ca,　Sr)　charge　compensated　by　Na+.　The　results　of　first-principles　calculations　for　4f　-＞　5d　excitations,　Stokes　shifts,　and　the　relative　position　of　5d　levels　to　conduction-band　edge　agree　well　with　experiments.　The　moderate　computational　cost　of　the　present　scheme,　which　can　be　applied　in　efficient　prediction　of　the　optical　properties　of　many　different　Ce-doped　materials,　is　of　important　value　in　screening　potential　lanthanide-doped　scintillators　and　phosphors　from　minimal　information　about　the　host　crystal　structure.