SMS Character Limits: GSM-7 vs. Unicode and How Messages Split Into Segments
October 21, 2026
A text message (SMS) is limited by the technology that carries it. A single SMS can carry 140 bytes of data. When the message uses the GSM-7 alphabet, which covers basic Latin letters, digits, and common punctuation at 7 bits per character, this fits 160 characters. If the message contains any character outside GSM-7, such as most emojis, curly quotes, or many non-Latin scripts, the whole message is encoded in UCS-2 (a Unicode encoding) at 16 bits per character, so a single message holds only 70 characters.
Longer messages are split into segments, each carrying a small header that reduces capacity: 153 characters per segment for GSM-7 and 67 for Unicode. Businesses pay per segment, so knowing the limits helps control cost.
Skip the math and get your answer instantly:
Open the Character Counter →Segment Math
For GSM-7: a message up to 160 characters is 1 segment. Over 160, each segment holds 153 characters, so 300 characters need 2 segments (300 ÷ 153 = 1.96, rounded up), 500 characters need 4 segments, and 459 characters fit in exactly 3. For Unicode: up to 70 characters is 1 segment; over 70, each segment carries 67 characters, so 150 characters need 3 segments and 300 need 5.
A single emoji in an otherwise plain 160-character message switches the entire message to Unicode encoding, so it needs 3 segments (160 ÷ 67 = 2.4, rounded up), tripling the cost.
| Message length | GSM-7 segments (153 per part) | Unicode segments (67 per part) |
|---|---|---|
| 70 characters | 1 | 1 |
| 160 characters | 1 | 3 |
| 300 characters | 2 | 5 |
| 459 characters | 3 | 7 |
| 500 characters | 4 | 8 |
What Breaks GSM-7
GSM-7 includes letters, digits, the basic punctuation marks, and some accented European characters, but not all. A few characters, like the euro sign, square brackets, curly braces, and the tilde, count as two characters because they use an escape sequence. Smart quotes and long dashes pasted from a word processor are not in GSM-7 and silently trigger Unicode. Emojis, Chinese, Japanese, Korean, Arabic, and Cyrillic text also use Unicode.
A simple practice is to type plain straight quotes and hyphens when writing SMS, and to preview the segment count in your messaging tool before sending.
Cost and Planning
Providers charge per segment, typically fractions of a cent to a few cents depending on country and volume. A campaign sending 100,000 messages at a 1-segment cost of $0.01 costs $1,000. If the message accidentally uses Unicode and runs to 3 segments, the cost rises to $3,000. Trim the copy to fit in one segment where possible. Put the key message first, since links and opt-out text consume characters. Use URL shorteners carefully, as they may affect deliverability and trust.
Carriers also apply filtering rules and registration requirements for business messaging in many countries; follow local regulations for consent and opt-out language.
Modern Messaging Alternatives
Many phones now use rich messaging (RCS) and apps such as WhatsApp, which have much higher limits and support media. When recipients can receive those, character limits are less of a concern. But SMS remains a universal fallback, and it still dominates for notifications and verification codes, so the limits still matter.
Frequently Asked Questions
How many characters are in one SMS?
160 using GSM-7 or 70 using Unicode.
Why does an emoji make my text cost more?
It forces Unicode encoding, which reduces the characters per segment to 70 or 67.
How many segments is a 300-character message?
2 in GSM-7 and 5 in Unicode.
Why are segments 153 characters rather than 160?
Each part of a multi-part message includes a header that takes up space.
How can I avoid Unicode?
Avoid emojis, smart quotes, and special characters, and preview the message before sending.