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SMS Segment Calculator

Free SMS segment counter and character counter for GSM-7 and UCS-2 encoding. Instantly calculate SMS length, segment count, and message costs. Perfect Twilio segment calculator for developers. Built by Blooio - the best way to send iMessages from anywhere.

Encoding

Auto: Uses GSM-7 when possible, UCS-2 for non-GSM characters
GSM-7: 7-bit encoding, 160 chars/SMS, basic Latin + symbols
UCS-2: 16-bit encoding, 70 chars/SMS, supports all Unicode

110,000

SMS Segment Details

Encoding:GSM-7
Segments:0
Total Size:0 bytes
Characters:0
Estimated Cost:$0.0000

Character Counter

0/160
Single segment160 remaining

Copy & Export

Cost Estimation

Current rate:$0.0083 per SMS
⚠️ Note: Twilio pricing does not include carrier fees. Additional fees may apply for A2P registration, toll-free verification, and carrier pass-through charges. View full pricing details
0 segments × $0.0083$0.0000

Text Segmentation Preview

Message segments will appear here

Hex Encoded Segments

Hex representation of message segments will appear here

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About SMS Segment Calculation

What is an SMS Segment Calculator?

An SMS segment calculator (also called a text segment calculator or message segment counter) is an essential tool for developers and businesses sending SMS messages through APIs. It calculates how many message segments your text will consume based on character count and encoding type (GSM-7 or UCS-2). Since SMS providers like Twilio charge per segment, this Twilio segment calculator helps you estimate costs accurately.

How SMS Segments Work

SMS messages have strict character limits that depend on the encoding type:

  • GSM-7 encoding: 160 characters in a single segment, 153 characters per segment in multi-part messages
  • UCS-2 encoding: 70 characters in a single segment, 67 characters per segment in multi-part messages

Multi-part messages use 6-7 bytes for concatenation headers, which is why the character limit is reduced. Our segment calculator automatically detects which encoding your message requires and calculates the exact number of segments.

Why Use a Twilio Segment Calculator?

When using Twilio or other SMS APIs, accurate segment counting is crucial for cost management and message optimization. This Twilio SMS segment calculator shows you not just the segment count, but also header bytes, payload size, and hex representation - all essential for debugging SMS gateway integrations and understanding exactly what you're sending.

Frequently Asked Questions

What is an SMS segment calculator?▼

An SMS segment calculator is a tool that helps you determine how many message segments your text will use. SMS messages are limited to 160 characters for GSM-7 encoding or 70 characters for UCS-2 (Unicode). Messages longer than these limits are split into multiple segments with additional header bytes.

How does the Twilio segment calculator work?▼

The Twilio segment calculator analyzes your message text to determine the encoding type (GSM-7 or UCS-2), counts characters, and calculates how many segments will be used. It also shows header bytes, total payload bytes, and hex representation - crucial information for SMS API implementations with Twilio and other providers.

What's the difference between GSM-7 and UCS-2 encoding?▼

GSM-7 is a 7-bit encoding that supports 160 characters per segment for basic Latin characters. UCS-2 is a 16-bit Unicode encoding that supports 70 characters per segment and is required for emojis, special characters, and non-Latin scripts. Multi-part messages use 153 characters (GSM-7) or 67 characters (UCS-2) per segment due to header overhead.

Why do I need a message segment counter?▼

A message segment counter helps you optimize SMS costs and delivery. SMS providers like Twilio charge per segment, so knowing your segment count before sending helps estimate costs. It also helps ensure your messages fit within carrier limits and display properly to recipients.

How many characters fit in one SMS segment?▼

Single SMS segments contain 160 characters for GSM-7 encoding or 70 characters for UCS-2 (Unicode). Multi-part messages have reduced capacity: 153 characters per segment for GSM-7 or 67 characters per segment for UCS-2, due to the concatenation header (6-7 bytes) required to reassemble the message.

What is the maximum SMS length?▼

There is no hard maximum SMS length - messages can be concatenated into multiple segments. However, most carriers support up to 10 segments (1530 GSM-7 characters or 670 UCS-2 characters). Single SMS messages are limited to 160 characters (GSM-7) or 70 characters (UCS-2). Use this SMS length calculator to check your message size.

What characters cause UCS-2 encoding?▼

Characters outside the GSM-7 character set trigger UCS-2 encoding. This includes emojis, smart quotes (curly quotes), special Unicode punctuation, and non-Latin alphabets like Chinese, Arabic, or Cyrillic. Common culprits are curly apostrophes (') and em dashes (—) copied from word processors. Our SMS character counter will highlight these problematic characters.

How do SMS segments affect cost?▼

SMS providers like Twilio charge per segment sent. A 161-character GSM-7 message costs twice as much as a 160-character message because it requires 2 segments. Using UCS-2 encoding (for emojis or special characters) can triple or quadruple your costs since each segment only holds 70 characters. Use our segment calculator to estimate costs before sending.

What is an SMS segment?▼

An SMS segment is a single unit of a text message as defined by the SMS protocol. Each segment has a maximum size of 140 bytes. For GSM-7 encoding, this allows 160 characters per segment. For UCS-2 Unicode encoding, this allows 70 characters per segment. Longer messages are split into multiple segments and reassembled on the recipient's phone.

SMS Length Calculator & Character Counter

Why SMS Length Matters

Understanding your SMS message length is critical for cost optimization and deliverability. This SMS length calculator helps you see exactly how your message will be segmented and charged by providers like Twilio, Vonage, Plivo, and MessageBird. Every character counts when you're sending thousands of messages.

SMS Character Counter Features

Our SMS character counter and Twilio character counter provides real-time analysis of your messages:

  • Character count - Total characters including spaces and special characters
  • Segment count - How many SMS segments your message will use
  • Encoding detection - Automatic GSM-7 or UCS-2 encoding identification
  • Problem character highlighting - Identifies characters forcing UCS-2 encoding
  • Byte-level analysis - Header bytes, payload bytes, and hex representation

SMS Length Limits Quick Reference

EncodingSingle SMSMulti-part (per segment)Max (10 segments)
GSM-7160 chars153 chars1,530 chars
UCS-2 (Unicode)70 chars67 chars670 chars

What is an SMS Segment?

An SMS segment is the fundamental unit of text messaging defined by the SMS protocol (Short Message Service). Understanding SMS segments is essential for anyone working with SMS APIs or managing messaging costs.

Technical Definition

Each SMS segment has a maximum payload of 140 bytes (1120 bits). Due to different character encodings, this translates to different character limits:

  • GSM-7 encoding: 7 bits per character = 160 characters per segment
  • UCS-2 encoding: 16 bits per character = 70 characters per segment

How SMS Segmentation Works

When your message exceeds a single segment, carriers use concatenated SMS (also called long SMS or multipart SMS). The message is split into multiple segments, each with a User Data Header (UDH) that contains:

  • Reference number to identify the concatenated message
  • Total number of segments
  • Sequence number for reassembly

This header consumes 6-7 bytes, reducing available characters to 153 (GSM-7) or 67 (UCS-2) per segment. This SMS segmentation tool automatically accounts for these headers.

Use Cases for This SMS Calculator

For Developers

  • Twilio SMS integration testing
  • API message payload debugging
  • Cost estimation for SMS campaigns
  • Character encoding validation
  • Twilio segment counter verification
  • SMS length validation before API calls

For Businesses

  • SMS marketing message optimization
  • Bulk SMS cost calculation
  • Multi-language message planning
  • Compliance and character limits
  • Message template optimization
  • SMS segment cost estimation

How to Use This Text Segment Calculator

Step 1: Enter Your Message

Type or paste your SMS message into the text area. The segment counter will automatically analyze your text in real-time as you type.

Step 2: Review Segment Count

Check the SMS Segment Details panel to see how many segments your message will use. The SMS calculator shows encoding type (GSM-7 or UCS-2), total characters, and data size.

Step 3: Optimize if Needed

If your message uses more segments than expected, enable Smart Encoding to automatically convert Unicode punctuation to GSM-7 characters. This message segment calculator feature can often reduce your message from UCS-2 to GSM-7 encoding, cutting costs significantly.

Step 4: View Technical Details

Scroll down to see the text segmentation preview and hex-encoded segments. This is particularly useful when integrating with Twilio or other SMS APIs, as you can see exactly how your message will be split and encoded.

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