A breakdown of voice over long term evolution (VoLTE) calls by adaptive multi-rate (AMR) speech coding mode may be determined by accessing a plurality of call detail records (CDRs) containing information associated with a plurality of corresponding communication sessions established over a mobile telephony network, and filtering the plurality of CDRs to obtain a subset of CDRs that are associated with communication sessions that used VoLTE services. A data structure containing correlations between AMR speech coding modes and bandwidth values may be referenced in order to classify the CDRs of the subset of CDRs into groups of different AMR speech coding modes. In some embodiments, a capacity planning metric or a resource allocation metric may be recommended based at least in part on numbers of the CDRs in the subset of CDRs within each of the groups of the different AMR speech coding modes.