How many characters are there to one message credit?

One message can contain up to and including 160 standard characters*, including spaces.

If you have more than 160 characters, this becomes a "multi-part" message, and each "part" has a limit of 153 characters (7 characters used by invisible headers and footers, indicating the part of the message being sent).

Once you have 161 standard characters or more, you will see your Credit Cost (per contact) increase (1),(2).

* The use of emoji's and unicode will affect character limits, i.e: the limit for one unicode message is 70; multi-part messages are 67 characters each. Find out more about this here.

Note: If you utilise the opt-out link it contributes to your character count.
The opt-out link is 29 standard characters, including spaces.

What is the maximum character limit for an SMS campaign?

You can send a maximum of 1600 standard characters*, or 11 credits per contact, per campaign.