SMS Segment Limits Guide

SMS

Understanding SMS Message Segments

When sending SMS messages, the number of characters that fit in one segment depends on how your message is encoded. The key point to remember is that the character limit per segment changes based on whether your message uses standard text or includes emojis and special characters.

Segment Limits by Message Type

Standard Text (GSM-7)

Messages with standard characters only (no emojis or special characters):
  • 1 segment: up to 160 characters
  • Longer messages: Messages that exceed 160 characters are automatically joined and use 153 characters per segment
    • 2 segments ≈ 306 characters
    • 3 segments ≈ 459 characters
    • And so on...

Unicode Messages (UCS-2)

Messages with emojis or non-GSM characters (e.g., emojis, accented characters, non-Latin scripts):
  • 1 segment: up to 70 characters
  • Longer messages: Unicode messages that exceed 70 characters use 67 characters per segment
    • 2 segments ≈ 134 characters
    • 3 segments ≈ 201 characters
    • And so on...

Examples

Example 1: Standard Text

Message: "Sale today only! Reply YES to claim."
  • Contains only standard characters
  • Uses GSM-7 encoding
  • Result: Up to 160 characters fit in 1 segment

Example 2: Message with Emoji

Message: "Sale today only! 🎉 Reply YES to claim."
  • Contains an emoji
  • Automatically uses Unicode encoding
  • Result: Only 70 characters fit in 1 segment. If you exceed 70 characters, your message will be split into multiple segments

Example 3: Mixed Content

Message: "👋 Hi Sarah, your appointment is tomorrow at 3:30pm. Reply YES to confirm."
  • Contains emoji and standard text
  • Uses Unicode encoding (because of the emoji)
  • Result: Once you go past 70 characters, each additional 67 characters creates another segment

Test Your Messages

You can test your own message content (with or without emojis) to see the exact encoding and number of segments before sending:

SMS Segment Calculator

0
Segments
0
Characters
GSM-7
Encoding
160
Remaining
GSM-7: 160 chars (single) / 153 per segment (multi)UCS-2: 70 chars (single) / 67 per segment (multi)
Simply paste your message content into the calculator to see how many segments it will use.

Test Your Messages using an API

If you’d rather perform test using our API, you can do so with the below API, just replace the text parameter with your text:
json
curl --location 'https://api.atomtel.com/api/atomic/sms/calculator' \
--header 'Content-Type: application/json' \
--data '{
    "text": "👋 Hi Sarah, your appointment is tomorrow at 3:30pm. Reply YES to confirm."
}'

Key Takeaways

  • Standard text messages: 160 characters per segment (153 for multi-segment messages)
  • Messages with emojis or special characters: 70 characters per segment (67 for multi-segment messages)
  • One emoji in your message will switch the entire message to Unicode encoding
  • Test your messages using the calculator link above to avoid surprises
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