What is the SMS Character Limit?

Learn about SMS character limits, why they exist, how to optimize messages, and manage costs for effective SMS marketing campaigns.

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SMS (Short Message Service) is a widely used communication tool, but it comes with notable constraints, particularly its character limits. This blog dives into the common questions about the SMS character limit, why they exist, and how they impact SMS marketing campaigns.

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How Long Can an SMS Text Be?

A standard SMS text message has a maximum of 160 characters when using the GSM character set, which includes basic Latin letters, numbers, and certain symbols. If your message includes Unicode characters—used for non-Latin scripts or special emojis—the limit decreases to 70 characters per SMS due to the additional data required for encoding.

Example:

• GSM Message (160 characters):
  “Don’t miss our weekend sale! Get up to 50% off on all items. Visit our website: www.shop.com.”
• Unicode Message (70 characters):
  “✨ Special Offer! Up to 50% off 🛍️ Visit: www.shop.com”
  
  

Notice how emojis and special characters reduce the available character count significantly.

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Why Is There a Limit on SMS Length?

The technology’s inception in the 1980s established the SMS character limit.. Dr. Friedhelm Hillebrand, one of SMS’s inventors, determined that 160 characters were sufficient to convey most short communications. The GSM protocol’s data constraints also dictated the limit.

When sending longer messages, the system breaks them into multiple parts, typically 153 characters each, as 7 bytes per part are reserved for concatenation headers to stitch the messages back together.

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What Happens If an SMS Exceeds the Limit?

When an SMS exceeds its character limit:

1. Segmented Messages: The system splits messages into smaller parts of 153 characters each.
2. Reassembly: The recipient’s phone combines these segments into one continuous message, provided all parts are received correctly.
3. Increased Costs: Telecom providers bill each segment separately, which impacts SMS marketing budgets.
   
   

For example, a 320-character message would be split into three SMS messages.

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What Are the Character Sets for SMS?

The GSM character set is the default for most SMS messages and supports 160 characters. It includes:

• Latin letters (A-Z, a-z)
• Numbers (0-9)
• Certain symbols like @, $, and !
  
  

When using Unicode characters, such as Chinese, Arabic, or emojis, the limit drops to 70 characters due to the need for extra encoding bytes.

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Why Does SMS Have a Character Limit While Apps Like WhatsApp Don’t?

SMS relies on the GSM protocol, which has strict limitations on data transmission. In contrast, apps like WhatsApp and iMessage operate over the internet and are not restricted by GSM’s constraints, allowing for longer messages without segmentation.

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How to Optimise SMS Messages Within Character Limits

Crafting effective SMS messages requires precision and creativity. Here are some practical tips:

1. Use an SMS Length Calculator
   Tools like a length calculator can ensure your message stays within the character limit, avoiding segmentation or added costs. For example, the Dripcel SMS length calculator lets you pre-test your campaigns.
   
   
2. Avoid Special Characters or Emojis
   Special characters, like #, @, or !, and emojis trigger Unicode encoding, which reduces the available character count. Instead, use text-based symbols or abbreviations where possible.
   
   
3. Craft Clear, Concise CTAs
   Always focus on a single key action. For example:
   • “Sign up for updates: www.shortlink.com” is better than “Please visit our website to learn more about signing up for updates and offers.”
     
     
4. Shorten Links to Save Space
   Use link-shortening tools like Bitly to conserve characters. For instance:
   • Original URL: “https://www.ecommerceplatform.com/sale-2024” (47 characters)
   • Shortened: “bit.ly/sale2024” (16 characters)

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The Cost Implications of Character Limits

SMS marketing campaigns aren’t just about crafting compelling messages—they’re also about managing costs. Here’s why character limits matter for your budget:

1. Segmented Messages Multiply Costs
   When an SMS exceeds 160 characters, it is broken into segments of 153 characters each (to reserve space for headers). For instance:
   • A 320-character message = 3 SMS segments.
   • If each SMS costs $0.05, the message will cost $0.15 to send to a single recipient.
     
     
2. Unicode Characters Add Up
   Unicode characters limit messages to 70 characters per SMS. A 320-character Unicode message would be split into 5 segments, significantly increasing costs.
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Example Cost Calculation:

• A campaign targeting 10,000 users:
  • GSM Message (160 characters): $500 (10,000 × $0.05)
  • Unicode Message (320 characters): $2,500 (10,000 × 5 segments × $0.05)
    
    

3. Efficiency is Key
   Crafting messages within the GSM character limit ensures cost-effectiveness and avoids splitting messages unnecessarily.
   
   

Pro Tip:

Regularly test your messages with tools like Dripcel’s SMS length calculator to maximise ROI.

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FAQs on SMS Character Limits

1. Can I send an SMS longer than 160 characters?
Yes, but it will be split into multiple segments, which are recombined on the recipient’s device.

2. Why are Unicode characters limited to 70 per SMS?
Unicode characters require more data for encoding, reducing the limit to 70 per message.

3. Does sending emojis count as Unicode?
Systems classify emojis and special symbols as Unicode characters, which reduces the character limit per SMS.

4. How does SMS marketing account for character limits?
Marketers often craft concise messages, avoiding unnecessary special characters or long links, to fit within the limits efficiently.

Key Terms to Remember

• SMS Character Limit: The maximum characters an SMS can contain (160 for GSM, 70 for Unicode).
• GSM Character Set: The default set of characters supported by SMS.
• Unicode Characters: Characters requiring additional encoding, reducing the SMS character limit.
• Length Calculator: A tool for determining the character count of your message.
  
  

By understanding SMS character limits, you can craft effective, compliant messages while optimising costs and engagement. Whether you’re sending a longer text or strategising your next SMS marketing campaign, respecting these limits ensures seamless communication and maximised ROI.