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Concatenated SMS

Community Manager
Community Manager

The character limit for one SMS is 160 characters. If you need to send a message longer than 160 characters, it is possible to send multiple SMS together, formed as a single, longer SMS; this is called a Concatenated SMS.


To join messages together to ensure they deliver as one, a 7-byte concatenation header is used at the beginning of each SMS. Since this header is within the message, it reduces the total size of each SMS to 153 characters each.


Please also be aware that if you are sending in Unicode, your character count per SMS lowers to 70 characters for a one-part message due to the fact that each UCS2 character requires 2 bytes. The 7-byte header for concatenated messages will also apply sending in excess of one message. As a result, a two-part Unicode message has a limit of 134 characters and a three-part Unicode message has a limit of 201 characters.


How will I be charged for Concatenated SMS


If you are sending concatenated SMS, you will be charged as follows:

  • a one-part message will allow you to send up to 160 characters - you are charged for 1 message.
  • a two-part message will allow you to send up to 306 characters - you are charged for 2 messages.
  • a three-part message will allow you to send up to 459 characters - you are charged for 3 messages.
  • and so on.

Concatenated Message Issues

If a user reports that the concatenated messages they are receiving on their mobile phones:

  • appear as separate messages
  • are being truncated
  • have message parts missing.

There are several reasons why a concatenated message (multi-part message) may not be correctly displayed on the handset:

  • The MT message parts arrived in the wrong order, which the handset is unable to process and display correctly.
  • The concatenated message is displayed as several separate text messages. This is usually due to the handset operating system, and its management process of the header information for each message part.
  • The handset may be busy, and the MT message part delivery may be postponed, which may cause the order of the message parts to be delivered in the wrong order. The operating system on most handsets, manage this scenario and wait until all message parts have been received, and then proceed to re-construct the message in the correct order, displaying the MT message as one complete message.

However, it is important to note that the order of the MT message part can change several times during transit, right up until the MT message part is delivered to the handset. This is due to routing technologies, load-balancing systems and re-try cycles, all of which have an impact on the delivery of the concatenated MT message.


Take a look at the Sinch SMS Product page to learn about Sinch's SMS products, or click here to sign up to our self-service portal and get started  and send your first message today!


Shahzad Ismail
Head of Knowledge Management and Community Engagement, Sinch