The 160-character SMS limit is not arbitrary — it comes from a 1985 technical decision that shaped global communication. Here is why it exists, what happens when you go over it, and how to work within the limit.
Why Is SMS Limited to 160 Characters?
In 1985, German engineers Friedhelm Hillebrand and Bernard Ghillebaert studied ordinary human communication and found that the average postcard and telex message was under 160 characters. They proposed using 160 characters as the limit for a new mobile messaging system — enough for a meaningful message, small enough to fit in signalling channels already used by mobile networks.
This 160-character limit (using GSM 7-bit encoding) has remained the global standard ever since, even though technology has advanced enormously.
SMS Character Limits at a Glance
| Encoding | Characters Per SMS | When Used |
|---|---|---|
| GSM-7 (standard) | 160 characters | English and basic Latin characters |
| Unicode (UCS-2) | 70 characters | Emoji, non-Latin scripts (Chinese, Arabic, etc.) |
| Concatenated SMS (GSM-7) | 153 chars per segment | Messages over 160 chars |
| Concatenated SMS (Unicode) | 67 chars per segment | Long messages with emoji/special chars |
What Happens When You Go Over 160 Characters?
When a message exceeds 160 characters, it is automatically split into multiple SMS messages and reassembled on the recipient’s device. However, each segment uses 7 characters for a header (to tell the phone how to reassemble the message), reducing the usable content per segment to 153 characters.
So a 170-character message actually sends as two SMS messages of 153 + 17 characters. This matters for two reasons:
- Cost: Mobile carriers charge per SMS segment. A 300-character message costs twice as much as a 160-character message.
- Delivery order: On some networks and older devices, segments can arrive out of order.
The Emoji Problem: Unicode Encoding
Adding a single emoji to your SMS switches the encoding from GSM-7 to Unicode (UCS-2). This drops your character limit from 160 to just 70 characters.
A single emoji in a 140-character message (which would normally be one SMS) pushes it to Unicode encoding, making it a two-segment message at 67+73 characters.
GSM-7 Extended Characters
The GSM-7 character set includes the standard Latin alphabet, numbers, and common punctuation. However, some characters that look standard are not in GSM-7 and will trigger Unicode encoding:
- Curly quotes (‘ ’ “ ”) — use straight quotes instead (' ")
- Em dash (—) — use double hyphen (--) instead
- Ellipsis (…) — use three separate periods (...) instead
- Non-breaking spaces
Checking SMS Character Count
Use our character counter to check your SMS text. The platform shows your character count live as you type, with the SMS limit (160) displayed in the platform character limits section.