Compute true on-the-wire RTP bandwidth per call including RTP, UDP, IP and layer-2 framing overhead.
A codec's headline rate only covers the audio. Every packet also carries a 12-byte RTP header, an 8-byte UDP header, a 20-byte IPv4 header and the layer-2 framing, and that fixed cost is paid at the packet rate. Shorter packetisation intervals mean more packets per second and proportionally more overhead. The overhead is not a rounding error: G.711 is 64 kbps of audio but 87.2 kbps on Ethernet, so a link sized on codec rates alone is 36% short.
RTP Bandwidth
bandwidth = (payload bytes + RTP 12 + UDP 8 + IP 20 + layer-2 bytes) × 8 × packets per second.
bandwidth = (payload bytes + RTP 12 + UDP 8 + IP 20 + layer-2 bytes) × 8 × packets per second. A codec's headline rate only covers the audio. Every packet also carries a 12-byte RTP header, an 8-byte UDP header, a 20-byte IPv4 header and the layer-2 framing, and that fixed cost is paid at the packet rate. Shorter packetisation intervals mean more packets per second and proportionally more overhead.
The overhead is not a rounding error: G.711 is 64 kbps of audio but 87.2 kbps on Ethernet, so a link sized on codec rates alone is 36% short.
This calculator takes 4 inputs: Codec payload rate, Packetisation interval, Layer-2 framing, Concurrent RTP streams. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.