The way your commercial SMS messages are constructed influences how they are sent and received. Before validating your dispatches, it is necessary to know some basic principles, especially the number and type of possible characters. Understanding the rules governing commercial SMS will indeed help you avoid some unpleasant surprises. Let’s delve together into the subject of SMS length.

How many characters in an SMS?

The total number of characters allowed varies depending on the type of characters placed in your commercial SMS.

building sms well number characters

The classic SMS (GSM-7)

By classic SMS, we mean here SMS using 7-bit encoding. These can therefore contain a maximum of 160 characters in total (spaces included). Beyond this number, the SMS will be divided into several messages and charged more:
160 characters = 1 sms charged
More than 160 characters = several sms charged
In brief:

  • 160 GSM alphabet characters allowed for the message (including certain special characters)
  • 11 characters allowed for the header (no special characters)
  • 20 characters allowed for the redirection URL

Apart from the letters of the Latin alphabet (in uppercase and lowercase), it is possible to place numbers in your messages, as well as some special characters.

GSM characters allowed:

@ £ $ ¥ è é ù ì
ò Ç Ø ø Å å
Δ _ Φ Γ Λ Ω Π Ψ
Σ Θ Ξ ^ { } \ [
~ ] | Æ æ ß É
! # ¤ % &
( ) * + , . /
0 1 2 3 4 5 6 7
8 9
: ; < = > ? ¡
Ä Ö Ñ Ü § ¿
a b c d e f g h
i j k l m n o p
q r s t u v w x
y z
ä ö ñ ü à
GSM characters allowed, but charged as 2 characters:
\ [ ] { } ~ ^ |

The Unicode SMS (UCS-2/UTF-16)

If you use in your message a character not listed in the 7-bit coding list, your message switches to Unicode mode. For the Unicode SMS, it is a message using 16-bit encoding. In this case, the total number of characters is much more restricted, with only 70. Here, it is a question of characters from non-Latin alphabets (Chinese, Arabic, Cyrillic, etc.) or special characters like emojis or particular symbols. This allows to send messages in all languages of the world, including certain regional dialects, but also to allow some fantasies, notably with emoticons.

Good to know

  • Be careful, remember that now the STOP SMS mention is mandatory in all commercial SMS. So you will have to subtract this same mention from the number of authorized characters when you construct your message. As for informative SMS, there is obviously no need for the “STOP SMS”, so we keep the number of authorized characters as a base.
  • To help you, some websites provide SMS length calculators. However, be aware that most platforms specialized in sending commercial SMS indicate the exact number of characters as you write the message.
  • For the redirection link, it is highly recommended to use a tool to shorten the URL.
  • Also, don’t forget that inserting personalization fields in your SMS can add non-GSM coded characters, which may result in additional costs.
  • Be aware that if you use a single character outside the GSM character set, your message will be divided into several messages if you exceed 70 characters.

The limitation of the number of characters allowed in SMS once again proves how important it is to design a short, precise, clear, and impactful message. This will not only allow you to respect the imposed limits, but also to send a message that is both easy to remember and as impactful as possible.



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