Good To Know – SMS Invitations
How SMS Segmentation and Credits Are Calculated
Each SMS has a fixed character limit. Messages that exceed this limit are automatically divided into smaller parts before delivery. SMS credits are calculated based on the standard SMS counting method described below. Understanding how this works helps you estimate how many SMS credits a message will use.
How it works:
- A message of 160 characters or fewer is sent as a single SMS and counts as 1 SMS credit.
- A message that exceeds 160 characters cannot fit in a single SMS and is split into a multi-segment message:
- Each segment holds up to 153 characters. The remaining characters in every segment are reserved to link the segments together so they reassemble correctly on the recipient’s device.
- SMS credits are deducted based on the total number of segments required. For example, a message split into three segments of 153 characters each uses 3 SMS credits.
- The character count includes everything in the final message — the content, the participation link, the sender identity, the unsubscribe message, and any text added through mail merge. The character count shown at the bottom of the SMS Content field on the Customize SMS Template wizard consists of all these elements combined.
- Standard text (letters, numbers, and common punctuation): up to 160 characters in a single SMS, or 153 characters per segment.
- Unicode characters (special characters such as emojis 😊, accented letters like é or ñ, and symbols like € or ™) use a different encoding with lower limits — up to 70 characters in a single SMS, or 67 characters per segment. As a result, these messages may use more segments, and more SMS credits, than standard-text messages of the same length.
Refer to the examples in the table below to better understand how SMS segments and credit deductions are calculated.
| Message length | Number of segments | SMS credits deducted | Why |
| 90 characters | 1 | 1 | The message is under the 160-character limit, so it fits in a single SMS. |
| 160 characters | 1 | 1 | This is exactly the single-message limit, so it still counts as one segment. |
| 175 characters | 2 | 2 | The message exceeds 160 characters, so it becomes multi-segment. Each segment holds up to 153 characters (153 + 22). |
| 300 characters | 2 | 2 | Two segments cover up to 306 characters (153 × 2), so 300 characters fit within two segments. |
| 320 characters | 3 | 3 | The message exceeds the 306-character capacity of two segments, so a third segment is required (153 × 3 = 459 capacity). |
| 90 characters (with a Unicode character) | 2 | 2 | Including a Unicode character (such as an emoji or symbol) switches the message to Unicode encoding, where a single SMS allows only 70 characters. Since 90 exceeds 70, the message splits into two segments of up to 67 characters each. |
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