WordCounter

SMS Character Counter

SMS character counter online. Calculate message segments, detect GSM-7 vs UCS-2 Unicode characters, and optimize text message lengths to eliminate carrier overages.

CURRENT SEGMENT LIMIT
0 / 160
REMAINING CHARS TO NEXT SEGMENT
160
SMS SEGMENTS
0
TOTAL SMS CHARS
0
ENCODING
GSM
UNICODE CHARS
0
0 chars•0 words

SMS Preview

0 segments
Segment 1 of 1 • 0 chars
Used
Empty
Unicode
Extended

The Definitive Guide to SMS Character Limits, Encoding & Segment Math

Short Message Service (SMS) remains the most universally supported and highest-engagement messaging channel in the world, boasting open rates exceeding 98%. However, behind the simple text bubble lies a technical architecture governed by strict telecom constraints established in the 1980s. When developing mobile apps, configuring two-factor authentication (2FA), or deploying SMS marketing campaigns, overlooking how characters are encoded can double or triple your billing overhead. Our free sms character counter and sms character counter online analyzes your text in real time to calculate billable segments and highlight expensive Unicode characters.

GSM-7 vs. UCS-2 Unicode: The 160 vs 70 Rule

Cellular standards define two primary encoding schemes for text messages:

  • GSM 03.38 (7-Bit Encoding): The default cellular standard packs 160 characters into a 140-byte transmission payload. It covers English letters, numerals, standard punctuation, and Greek capital letters.
  • UCS-2 (16-Bit Unicode): When any character outside the GSM-7 table is typed (such as emojis, Cyrillic, Arabic, or curly quotes), the carrier switches to 16-bit encoding, dropping single segment capacity from 160 down to only 70 characters.
  • The "Rogue Character" Trap: Copying text from Word or Google Docs often brings along smart curly apostrophes (’) instead of straight ASCII apostrophes ('), quietly quadrupling your campaign costs without you realizing it.

Concatenation and the Hidden User Data Header (UDH)

What happens when an SMS text message exceeds a single segment:

  • The 7-Byte Header: When messages are concatenated, carriers reserve 6 to 7 bytes (equivalent to 7 GSM characters or 3 Unicode characters) per segment to transmit routing instructions that tell the receiving device how to assemble the pieces.
  • GSM-7 Concatenated Limit: In multi-part GSM messages, each segment carries 153 characters rather than 160.
  • UCS-2 Concatenated Limit: In multi-part Unicode messages, each segment carries 67 characters rather than 70.

SMS Segment Breakdown: GSM-7 vs. UCS-2 Unicode

Segments BilledGSM-7 Character CapacityUCS-2 Unicode CapacityCost Multiplier
1 Segment1 – 160 characters1 – 70 charactersBase Rate (1x)
2 Segments161 – 306 characters71 – 134 charactersDouble Cost (2x)
3 Segments307 – 459 characters135 – 201 charactersTriple Cost (3x)
4 Segments460 – 612 characters202 – 268 charactersQuadruple Cost (4x)

Related Topics & Search Queries: skype sms character counter.

Frequently Asked Questions

How many characters are in a standard SMS text message?

A standard SMS encoded in GSM-7 allows up to 160 characters in a single segment. If your message exceeds 160 characters, it is broken down into multi-part concatenated segments of 153 characters each (7 characters are reserved for the technical User Data Header that instructs the recipient phone how to reassemble the message).

Why did my SMS segment limit suddenly drop to 70 characters?

If you type even a single non-GSM character—such as an emoji (😊), a smart curly quote (“ ”), an em dash (—), or non-Latin alphabet characters—telecom carriers are forced to switch the message encoding from 7-bit GSM-7 to 16-bit UCS-2 (Unicode). UCS-2 restricts messages to only 70 characters per single segment (and 67 characters per segment when concatenated).

What is a concatenated SMS and how does it work?

Concatenated SMS (also known as multi-part or long SMS) occurs when a message exceeds the single-segment capacity. Cellular networks split the text into chunks and prepend a hidden User Data Header (UDH) so the receiving smartphone seamlessly displays it as a single cohesive text bubble.

How do SMS segments affect SMS marketing and API costs?

Cellular carriers and SMS gateways (such as Twilio, Sinch, Vonage, and AWS SNS) bill per individual segment, not per text bubble. A single emoji that triggers UCS-2 encoding can triple your campaign costs by turning a 1-segment message into 3 billed segments.

Can I use this tool to optimize marketing campaigns and customer alerts?

Yes! By pasting your automated transactional texts or promotional marketing copy into this SMS character counter online, you can immediately identify expensive rogue Unicode characters and keep your message within a single 160-character segment.