VoIP Bandwidth Calculator (Codec, Packet Size and Headers)
Real network bandwidth of a voice call from the codec bit rate, packet interval, IP version and link layer, and the total for several calls — in each direction.
Results
What this tool does
A G.711 voice stream is 64 kbit/s inside the codec but needs 87.2 kbit/s on Ethernet at 20 ms per packet, because the 40 bytes of IP, UDP and RTP headers plus 18 of Ethernet are sent 50 times a second. The overhead hits low-rate codecs hardest: G.729 at 8 kbit/s grows to 31.2 kbit/s, almost four times. Longer packet intervals cut the headers but add delay and make each lost packet more audible. Silence suppression and RTCP are not included.
Formula
payload = bit rate × interval ÷ 8 · packet = payload + IP/UDP/RTP + link header · bandwidth = packet × 8 × (1000 ÷ interval) (per direction)
Variables
| Symbol | Meaning | Unit |
|---|---|---|
rt | Codec bit rate | kbit/s |
pt | Packetisation interval (voice per packet) | ms |
ip | Network headers | — |
l2 | Link layer | — |
nc | Simultaneous calls | — |
BW | Bandwidth of one call, each direction | kbit/s |
PL | Voice bytes per packet | bytes |
PK | Packet size on the wire | bytes |
PP | Packets per second | /s |
OV | Share of the bandwidth that is headers | % |
TT | All the calls together, each direction | kbit/s |
Worked example
- Codec bit rate64 kbit/s
- Packetisation interval (voice per packet)20 ms
- Network headers40
- Link layer18
- Simultaneous calls10
- Bandwidth of one call, each direction87.2 kbit/s
- Voice bytes per packet160.0 bytes
- Packet size on the wire218.0 bytes
- Packets per second50.0 /s
- Share of the bandwidth that is headers26.6 %
- All the calls together, each direction872 kbit/s
Limitations
- The formula assumes ideal conditions: no friction losses, no air resistance and no efficiency losses unless you enter them.
- The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.