Calculate the number of concurrent SIP channels supported by available bandwidth.
A SIP trunk channel's total bandwidth footprint is the RTP media stream (governed by the chosen codec plus RTP/UDP/IP overhead) plus the SIP signaling traffic needed to set up, maintain, and tear down the call (INVITE, ACK, re-INVITEs for hold/transfer, BYE). While signaling is a small fraction of a call's total bandwidth compared to media, it still counts against the link's total capacity and should be included when sizing exactly how many concurrent channels a SIP trunk's bandwidth allocation can support.
Max concurrent channels
channels = bandwidth_kbps / (codec_rate_kbps + sip_overhead_kbps)
Each active call generates its own independent stream of SIP signaling messages (its own INVITE/ACK/BYE and any mid-call re-INVITEs), so signaling bandwidth scales with the number of concurrent calls, not as a single fixed cost for the trunk — amortizing it per channel gives an accurate total bandwidth estimate at any given channel count.
Typically these are negligible and not counted per-channel since they occur at a fixed, low frequency (e.g. every 30-60 seconds) regardless of call volume — this calculator focuses on per-call signaling overhead (INVITE through BYE) which is the dominant, volume-scaling component.
Provision for your busy-hour peak concurrent call count (derived from Erlang B/C analysis) plus a safety margin — many SIP trunk providers also sell channels in fixed increments, so round up to the provider's next available tier rather than provisioning the exact calculated minimum.