RTP Bandwidth Calculator
Compute true on-the-wire RTP bandwidth per call including RTP, UDP, IP and layer-2 framing overhead.
About RTP Bandwidth Calculator
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
Worked example
With the default values below, RTP Bandwidth Calculator returns Bandwidth per Stream of 87.20. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Codec payload rateaccepts 4–1,024 kbps
- 64 kbps
- Packetisation intervalaccepts 5–120 ms
- 20 ms
- Layer-2 framingone of Ethernet — 18 B, Ethernet + 802.1Q — 22 B, PPPoE — 26 B, MPLS (2 labels) — 26 B, MLPPP/Frame — 6 B
- Ethernet — 18 B
- Concurrent RTP streamsaccepts 1–100,000 streams
- 1 streams
Results
- 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
Step by step
- 1Values used
- 2RTP Bandwidth
- 3Bandwidth per Stream= 87.20 kbps
- 4Packets per Second= 50
- 5Frame Size on the Wire= 218 bytes
- 6Overhead Share of the Frame= 26.6
- 7Total for All Streams= 0.09 Mbps
Assumptions and limits
- The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax or compounding frequency into account.
- Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
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.