SMS Character Limits: How Text Message Length and Pricing Work
SMS remains one of the most widely used communication channels, with over 6 billion text messages sent daily worldwide. Understanding character limits is crucial because exceeding them splits your message into multiple parts, each billed separately.
SMS Character Limit Trivia
The original 160-character SMS limit was determined by Friedhelm Hillebrand in 1985. He analyzed postcards and telex messages, finding that most communication could be expressed in under 160 characters. This limit was adopted as the GSM standard and has persisted for nearly four decades.
Why 160 Characters?
SMS uses GSM-7 encoding, representing each character in 7 bits. A single SMS segment carries 1,120 bits of payload, equaling exactly 160 characters. When Unicode characters (emoji, CJK characters) are used, encoding switches to UCS-2 at 16 bits per character, reducing the limit to 70 characters per segment.
SMS Character Limits
| Encoding | Single SMS | Multi-part SMS | Notes |
|---|---|---|---|
| GSM-7 (Latin) | 160 characters | 153 per segment | 7 chars reserved for concatenation header |
| UCS-2 (Unicode) | 70 characters | 67 per segment | Required for emoji, CJK characters |
Carrier Support and Limits
| Region | Max Segments | Max Characters (GSM-7) |
|---|---|---|
| US (most carriers) | Up to 10 | ~1,530 |
| Europe (typical) | Up to 6 | ~918 |
| Japan | Up to 10 | ~670 (Shift_JIS) |
SMS Pricing Structure
Each SMS segment is billed individually. A 161-character GSM-7 message becomes two segments, doubling the cost. For business SMS campaigns, this has significant budget implications. A single emoji forces Unicode encoding, cutting your limit to 70 characters per segment.
Business SMS Best Practices
- Stay under 160 characters: Keep messages to a single segment whenever possible
- Avoid emoji in transactional SMS: A single emoji forces Unicode encoding
- Use URL shorteners: Long URLs consume valuable character space
- Include opt-out instructions: Regulatory requirements consume characters but are legally required
- Test across carriers: Message rendering varies between carriers and devices
Common Mistakes
- Accidental Unicode: Smart quotes or special dashes trigger UCS-2 encoding, unexpectedly halving your character limit
- Ignoring concatenation overhead: Multi-part messages lose 7 characters per segment to the header
- Not counting invisible characters: Line breaks and special whitespace count toward the limit
Conclusion
SMS character limits are rooted in decades-old encoding standards that still govern modern messaging. Understanding the difference between GSM-7 and Unicode encoding is essential for cost-effective messaging. Use Character Counter to verify your SMS length before sending.