VoIP Bandwidth Calculator
A G.711 call is quoted as 64 kbps and actually costs about 87 kbps on Ethernet, because RTP, UDP, IP, and the frame headers are charged on every packet — and at 20 ms packetisation that is fifty packets a second. Pick the codec, packetisation interval, and link type to get the figure to size a trunk with.
Payload rate kbps
packets/second
cRTP compresses the RTP/UDP/IP header the ESP tunnel then encrypts — in practice you get one or the other, not both. The figure below assumes compression happens first.
Per call, one direction
calls, both directions
- Voice payload
- RTP + UDP + IP
- Layer 2 overhead
- Total frame size
- Packets per second
- Overhead share
Voice is symmetric and full duplex, so a link carries the per-call figure in each direction simultaneously. Size an access circuit on the one-direction number; size a shared backhaul on the doubled one. Neither figure includes SIP signalling, which is negligible by comparison, or the RTCP stream, which is about 5%.