# What is a concatenated SMS?

> A concatenated (or multipart) SMS is a message longer than a single segment — 160 GSM-7 characters, or 70 in UCS-2 — split across multiple SMS parts and reassembled into one message on the handset. A User Data Header (UDH) in each part carries a reference number and sequence so the phone stitches them in order. Concatenation reduces the per-segment payload to 153/67 characters to make room for the UDH, and each part is billed separately. See /answers/what-is-udh-sms, /answers/what-is-encoding-gsm-7-ucs-2, and /tools/sms-segment-calculator.

- Canonical URL: https://www.broadnet.me/answers/what-is-concatenated-sms
- Language: en
- Last reviewed: 2026-07-22
- Publisher: BroadNet (https://www.broadnet.me)

## Related

- [All answers](https://www.broadnet.me/answers)
- [Glossary](https://www.broadnet.me/answers)
- [UDH — User Data Header in SMS explained](https://www.broadnet.me/answers/what-is-udh-sms)
- [What is a flash SMS?](https://www.broadnet.me/answers/what-is-flash-sms)
- [GSM 7-bit vs UCS-2 encoding — when each is used](https://www.broadnet.me/answers/what-is-encoding-gsm-7-ucs-2)
- [What is GSM-7 encoding?](https://www.broadnet.me/answers/what-is-gsm-7)
- [UCS-2 — Unicode SMS encoding explained](https://www.broadnet.me/answers/what-is-ucs-2-sms)
- [SMS segment calculator](https://www.broadnet.me/tools/sms-segment-calculator)
- [SMS API](https://www.broadnet.me/products/sms-api)
- [Bulk SMS](https://www.broadnet.me/products/bulk-sms)