One SMS credit is 160 characters long.
The amount of credits you need depends on the length of your SMS message and the size of your audience. For example, a single message (160 characters or less) to 50 contacts will count as 50 credits.
If you wish to send larger messages (over 160 characters) this will count as multiple credits per recipient. For example:
Up to 160 characters = 1 credit
Up to 306 characters = 2 credits
Up to 459 characters = 3 credits
Up to 612 characters = 4 credits
Top tip: The number of messages used will be displayed with our handy character counter in the app when you type out your message content.