Message Segment
SMS bills per segment: 160 plain characters, 153 concatenated, 70 with any emoji. Watch encoding or pay multiples per send.
Carriers transmit SMS in fixed-size segments, and every fee in the ecosystem — provider send price, carrier surcharge — applies per segment, not per message.
The math: a single SMS holds 160 characters in the GSM-7 alphabet. Longer messages are split and stitched (concatenated), with each part carrying 7 bytes of header, leaving 153 characters per segment. One emoji, smart quote, or non-GSM character switches the whole message to UCS-2 encoding: 70 characters per single message, 67 per concatenated segment.
A 320-character message with one emoji is 5 segments — five times the carrier surcharge of a trimmed 160-character GSM-7 message. At campaign scale, segment discipline is a real budget line.
Frequently asked questions
Related glossary terms
Carrier surcharges are per-segment fees ($0.0025-$0.01 typical) that US carriers charge on A2P SMS, passed through by providers on top of the base message price. Registered traffic pays lower rates than unregistered.
SMS throughput is the rate (messages per second) at which carriers accept a sender's traffic. Under 10DLC it is determined by brand trust score; short codes offer the highest fixed throughput.
10DLC (10-Digit Long Code) is the US carrier-mandated framework for sending Application-to-Person SMS from local 10-digit numbers, requiring brand and campaign registration with The Campaign Registry.