RTP Bandwidth Calculator
Compute true on-the-wire RTP bandwidth per call including RTP, UDP, IP and layer-2 framing overhead.
Inputs
Bandwidth per Stream
87.20kbps
Packets per Second
50
Frame Size on the Wire
218bytes
Overhead Share of the Frame
26.6%
Total for All Streams
0.09Mbps
Step by step
Values used
Codec payload rate = 64 kbps; Packetisation interval = 20 ms; Layer-2 framing = Ethernet — 18 B; Concurrent RTP streams = 1 streams
RTP Bandwidth
bandwidth = (payload bytes + RTP 12 + UDP 8 + IP 20 + layer-2 bytes) × 8 × packets per second.
Bandwidth per Stream
= 87.20 kbps
Packets per Second
= 50
Frame Size on the Wire
= 218 bytes
Overhead Share of the Frame
= 26.6
Total for All Streams
= 0.09 Mbps
How it works
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.
Formula
RTP Bandwidth
bandwidth = (payload bytes + RTP 12 + UDP 8 + IP 20 + layer-2 bytes) × 8 × packets per second.
- payload bytes
- codec rate × packetisation interval ÷ 8
- pps
- 1000 ÷ packetisation interval in ms
Frequently Asked Questions
How is RTP Bandwidth calculated?
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.
Why does RTP Bandwidth matter?
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.
What values do I need to enter?
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.