Calculate SMS throughput capacity for a messaging gateway or SMPP connection.
SMS throughput on a signaling channel is bounded by dividing the available bandwidth by the total size of each message, which includes both the SMS payload itself (up to 140 bytes/1120 bits for a single-segment message) and the signaling protocol overhead needed to route and deliver it (SS7/MAP headers for network-to-network delivery, or SMPP PDU overhead for application-to-SMSC connections). This models a dedicated signaling link; in practice SMS delivery also depends on SMSC processing capacity and downstream mobile network paging/delivery success rates.
SMS throughput
sms_per_sec = bandwidth_bps / (sms_size_bits + overhead_bits)
The original GSM SMS standard reserved a 140-byte (1120-bit) payload within a signaling message, which encodes to 160 characters using 7-bit GSM encoding, 140 characters using 8-bit encoding, or 70 characters using 16-bit UCS-2 encoding (needed for non-Latin scripts like Arabic, Chinese, or emoji) — longer messages are split into multiple linked segments, each consuming this same per-segment capacity.
SS7/MAP overhead applies to signaling between mobile network elements (MSC to SMSC, inter-carrier delivery) and is fairly fixed by the protocol standard. SMPP overhead applies to the connection between an application/aggregator and an SMSC (Short Message Service Center) and can vary based on optional TLV parameters used — both add meaningfully to the raw 1120-bit payload size when calculating real-world throughput.
Not always — modern SS7/SIGTRAN links and SMPP connections often have far more raw bandwidth than SMS traffic needs; the practical bottleneck is more often SMSC processing capacity (store-and-forward queuing, retry logic), per-connection throughput limits imposed by carriers/aggregators, or downstream mobile network congestion during high-volume campaigns.