The figures on this page show IP / UDP / RTP packet bandwidth and overhead requirements for a few popular voice codecs, including G.711, G.722, and G.729.
G.711 IP/UDP/RTP Packet Bandwidth and Overhead Calculation
G.722 IP/UDP/RTP Packet Bandwidth and Overhead Calculation
G.729A IP/UDP/RTP Packet Bandwidth and Overhead Calculation