SMS Character Count: GSM-7 and Unicode Limits Explained

Your SMS character count limit is 160 characters per message when the text uses the GSM-7 alphabet. That fits a 140-byte payload defined in 3GPP TS 23.038 and TS 23.040. Add one emoji, Urdu letter or curly quote and the whole message switches to Unicode, where the limit is 70 characters.

What counts as one SMS character?

One SMS character is one symbol from the GSM-7 alphabet, and a single SMS holds up to 160 of them.

GSM-7 alphabet basics

GSM-7 is the default 7-bit character set for SMS, defined in 3GPP TS 23.038. It covers unaccented Latin letters, digits, common punctuation and a limited set of accented letters and symbols. Seven bits per character is what lets 160 of them fit in one message.

A few symbols sit in an extension table and cost two characters each: € [ ] { } \ ^ ~ |. If your text uses them, your usable length is below 160.

Why 160 is the magic number

One SMS carries 140 bytes of data (TS 23.040). That is 1,120 bits, and 1,120 divided by 7 bits per character is 160. UCS-2, the Unicode encoding SMS uses, needs 2 bytes per character, so the same 140 bytes hold 70. The limit comes from the message format, not from the language you write in.

How Unicode cuts your limit to 70 characters

Unicode cuts the limit to 70 because every character takes 2 bytes instead of 7 bits.

A message uses one encoding for its whole text. One character outside GSM-7 moves every character to UCS-2, so a 100-character message with a single curly quote now exceeds the single-SMS limit of 70.

Which characters trigger Unicode mode

Any character missing from GSM-7 triggers it. The usual causes:

• Urdu, Arabic and other non-Latin letters.

• Emoji.

• Smart punctuation: curly quotes (‘ ’ “ ”), en and em dashes, and the single ellipsis character.

• Accented letters outside the GSM-7 set, such as á, í, ó and ú.

Why Urdu, emoji, and smart punctuation matter

The switch is silent and applies to the whole message. Your text looks the same on screen, but the limit falls from 160 to 70 and the segment count rises. A 160-character GSM-7 message in which one straight quote becomes a curly quote needs 3 segments instead of 1.

Urdu messages sit under the 70-character limit every time, so short copy matters. Many emoji also take two positions in UCS-2 because they sit outside its basic range, so they use up the 70 faster.

Multipart messages: segments and the 153/67 rule

A message longer than one SMS is split into segments of 153 GSM-7 characters or 67 Unicode characters each. The receiving phone joins the segments back into one message.

Why segments hold fewer characters than a single SMS

Each segment still carries 140 bytes, but part of that space holds a header. The header tells the phone which message the part belongs to, how many parts exist and which one this is. It uses 6 bytes (TS 23.040), leaving 134 bytes for text. That is 1,072 bits, or 153 GSM-7 characters, and 67 UCS-2 characters at 2 bytes each.

How segment count affects what you're billed for

Each segment travels as a separate SMS, so a provider that charges per SMS counts segments, not messages. Confirm how yours counts before a campaign. Examples:

• 160 GSM-7 characters: 1 segment.

• 161 GSM-7 characters: 2 segments (153 + 8).

• 307 GSM-7 characters: 3 segments (153 + 153 + 1).

• 70 Unicode characters: 1 segment.

• 71 Unicode characters: 2 segments (67 + 4).

The SMS cost estimator is the place to turn a segment count into a sending budget.

Full form and meaning of SMS

SMS stands for Short Message Service. The name describes the product: a service for sending short text messages between mobile phones. The first SMS was sent on 3 December 1992 by Neil Papworth, a Sema Group engineer, from a computer to Richard Jarvis at Vodafone. Its text was "Merry Christmas" (Vodafone). Browse more SMS guides for sending basics.

How to check your character count before sending

Paste the final text into a counter and compare its length with the limits above.

Using an SMS character counter

The SMS character counter tool on this site is the practical next step. Use it in this order:

1. Paste the exact text you will send, including the opt-out line and any link.

2. Replace merge fields with the longest value they can take, such as your longest customer name.

3. Check whether the text stays within 160 characters (GSM-7) or 70 (Unicode).

4. If it runs over, split it with the 153/67 rule and decide whether to trim or accept the extra segment.

Common mistakes that bump you into Unicode

• Curly quotes and apostrophes pasted from a word processor or added by a phone keyboard's auto-correct.

• Em dashes, en dashes and the single ellipsis character instead of three periods.

• Emoji, even one at the end of the text.

• Urdu, Arabic or other non-Latin script, even a single word.

• Accented letters outside GSM-7, such as á, í, ó and ú, in a pasted name.

Replace each with its plain equivalent: straight quotes, a hyphen, three periods. Remember that € [ ] { } \ ^ ~ | stay in GSM-7 but count as two characters each.

Where to get SMS sending and counting tools

You can get SMS sending tools from mobile operators, API platforms and messaging software. Many mobile operators sell a business SMS service, so ask yours what it offers. API platforms such as Twilio and Vonage let developers send SMS from code. Whichever you choose, ask how it counts segments and whether it rewrites smart punctuation before sending.

WaSMS is another option to compare. WaSMS is run by the same team as this site.

Check your exact character count and segment split before you send: open the SMS character counter tool.

How many characters are in one SMS message?

One SMS holds 140 bytes, which is 160 GSM-7 characters or 70 Unicode (UCS-2) characters, as set out in 3GPP TS 23.038 and TS 23.040. FreeSMSGateway lists the same limits on its SMS character counter page.

Why does my SMS character limit drop to 70?

One character outside the GSM-7 alphabet switches the whole message to Unicode (UCS-2), which stores each character in 2 bytes. The 140-byte SMS then holds 70 characters. Emoji, Urdu letters and smart punctuation such as curly quotes are the usual triggers.

What is the full form of SMS?

SMS stands for Short Message Service, the text messaging service built into mobile networks. The first SMS was sent on 3 December 1992 by Neil Papworth, and its text was Merry Christmas.

How many characters fit in a multipart SMS segment?

A multipart segment holds 153 GSM-7 characters or 67 Unicode characters. Each segment spends 6 of its 140 bytes on a header that lets the phone reassemble the message in order.

Do emojis reduce my SMS character limit?

Yes. An emoji forces the whole message into Unicode, so the limit falls from 160 to 70 characters per SMS and from 153 to 67 per segment. Many emoji also take two character positions, so check the count with an SMS character counter before you send.

Why do Urdu or Arabic characters change my character count?

Urdu and Arabic letters are not in the GSM-7 alphabet, so a message containing even one of them is sent as Unicode. That limits each SMS to 70 characters, or 67 per segment in a multipart message. A mixed English and Urdu text is counted the same way.