Avoid costly SMS: How characters are counted in a text

GSM-7 vs Unicode – what you need to know when sending SMS

GSM-7 is an efficient character encoding format for SMS messages, allowing up to 160 characters per message as long as all characters are part of the standard character set. If any characters fall outside of GSM-7 – such as emojis or certain special symbols – the system switches to Unicode, reducing the character limit to 70, which can significantly increase the cost. Even small details, like the length of a recipient’s name, can affect how many messages are sent – and ultimately, the total cost of a large-scale SMS campaign.

Switching from email or other forms of communication to SMS can feel like a big change – but SMS is a powerful channel with higher open rates and faster response times compared to email. Over 90% of SMS messages are opened within minutes, while emails can remain unread in inboxes for hours or even days.

• Promotions and offers
• Transaction and order notifications
• Bookings and reminders
• Security alerts
• Important updates to staff or customers

How to optimise your messages and manage character limits

A standard SMS message supports 160 characters if it uses GSM-7 – the most common encoding for Latin alphabets. If your message exceeds 160 characters (or 70 with Unicode), it will be split into multiple messages. Thanks to concatenation, the recipient will still see it as one continuous message, but you’ll be charged for each part. Here’s how longer messages are divided:

• 161–306 characters= 2 SMS
• 307–459 characters = 3 SMS
• 460–612 characters = 4 SMS

What counts towards the character limit?

It’s not just the message text that counts – other elements also affect the total number of characters:

• Sender ID: An alphanumeric sender ID (e.g. "LEKAB") can take up to 5 characters, while a short code (e.g. 72345) doesn’t affect the count.
• Links: Including a URL, e.g., "https://example.com/promo", adds the full link length to the count (around 33 characters). Use a URL shortener e.g., "https://short.url/3abcXYZ", to reduce it to approx. 20 characters.
• Hidden characters: Copying text from Word or other sources can include invisible characters that increase the total. Paste your text into a plain text editor (like Notepad) to clean it up before sending.

How to avoid sending more SMS than necessary

While GSM-7 is cost-effective and widely supported, it has limitations. Notably, it doesn’t support emojis or certain special characters, which can affect both the user experience and your brand tone.

Keep in mind:

• Using even one unsupported character (e.g. emoji or certain symbols) switches the entire message to Unicode, cutting the limit to 70 characters.
• Messages that exceed the character limit are split into multiple messages, increasing costs.
• Accidentally using an unsupported character can convert the whole message to Unicode, leading to higher charges.

What is GSM-7?

GSM-7 is the standard encoding for SMS messages and supports basic Latin characters (A-Z, a-z), numbers, and commonly used symbols. It’s the most cost-efficient option, allowing up to 160 characters per message.

GSM-7 supports:

• Latin letters (A-Z, a-z)
• Numbers (0–9)
• Common symbols (!, @, #, &, %, etc.)

Not supported (requires Unicode):

• Chinese
• Japanese
• Korean
• Arabic
• Hebrew
• Russian
• Greek
• Thai
• Indian languages

GSM-7 is the standard encoding used for SMS and contains basic Latin characters (GSM-7 is the standard encoding used for SMS and contains basic Latin characters (see the full table here)

What is Unicode and when is it used?

Unicode is used when a message contains languages or symbols not supported by GSM-7 – such as Chinese, emojis, or unique characters. The downside? Unicode reduces the message size to just 70 characters.

Examples:

• A message using only Latin letters (GSM-7) = 160 characters
• A message with one emoji (Unicode) = 70 characters
• Messages over 70 characters are split and billed accordingly

Unicode is used for languages ​​and symbols not supported by GSM-7, such as Chinese characters, emojis, and some special characters. Read more about Unicode here.

Want to maximise the impact of your SMS messages?

With the right strategy, SMS can become one of your most powerful communication tools. By using personalisation, smart timing, and analytics, you can ensure every message adds value and strengthens customer relationships.

RCS – The next generation of messaging (SMS 2.0)

RCS (Rich Communication Services) is the next-gen alternative to traditional SMS. It offers verified senders, high-resolution images, clickable buttons, and interactive elements. Messages can include up to 2000 characters, support emojis, rich media, and two-way communication.

RCS is particularly useful for marketing and customer support because it enables interactive messaging with images, videos, buttons, and two-way communication. Businesses can create engaging campaigns, send order updates, or handle customer inquiries right in the messaging app—without customers needing to download a separate app. 

At LEKAB, we have the tools and expertise to help you optimise your SMS and RCS communication. Whether you're looking to automate your messaging, boost engagement or increase conversions, we can guide you through the process.