Character Limits, Encoding & Cost Calculation
Understanding how SMS character length and encoding work helps you write clear messages while optimizing your credit consumption.
Core SMS Length Rules
Section titled “Core SMS Length Rules”| Rule | Limit / Value | Details |
|---|---|---|
| Single SMS Limit | 160 characters | Any message up to 160 GSM characters costs 1 SMS credit per recipient. |
| Multi-Part (Concatenated) Segment Size | 153 characters per part | When a message exceeds 160 GSM characters, 7 characters per part are reserved for concatenation headers (UDH), so each segment holds 153 characters. |
| Maximum Message Length | 1,000 characters | A single message submission can contain up to 1,000 characters (up to 7 concatenated SMS parts). |
Credit Calculation by Character Count
Section titled “Credit Calculation by Character Count”When your message exceeds 160 GSM characters, the total number of SMS parts (and credits per recipient) is calculated as:
SMS Parts = Math.ceil(Total GSM Characters / 153)| GSM Character Count | SMS Parts (Credits per Recipient) |
|---|---|
| 1 – 160 characters | 1 SMS part |
| 161 – 306 characters | 2 SMS parts |
| 307 – 459 characters | 3 SMS parts |
| 460 – 612 characters | 4 SMS parts |
| 613 – 765 characters | 5 SMS parts |
| 766 – 918 characters | 6 SMS parts |
| 919 – 1,000 characters | 7 SMS parts |