What Are the Character Limits for a Single SMS? Complete Guide

Understanding SMS Character Limits: Why It Matters

If you have ever typed out a message and wondered why it was split into two or three parts, you are not alone. Character limits for a single SMS are one of the most frequently asked questions in the messaging world, and honestly, they are more nuanced than most people realize.

Whether you are sending bulk SMS campaigns, time-sensitive OTP alerts, or marketing blasts, understanding character limits is essential. It directly impacts your messaging costs, delivery rates, and the overall experience your customers have when they receive your texts.

Let us break it all down in plain language so you can plan your campaigns smarter and avoid surprise charges.

The Basic SMS Character Limit: 160 Characters

At its core, a single SMS message supports 160 characters when using the standard GSM-7 encoding. This is the default character set that includes the Latin alphabet, numbers, and a handful of common symbols.

Here is a quick look at what falls under GSM-7 encoding:

• All English letters (uppercase and lowercase): A–Z, a–z
• Numbers: 0–9
• Common punctuation: periods, commas, exclamation marks, question marks
• Special characters: @, #, $, %, &, *, and a few others
• Spaces and line breaks

So if your message reads something like "Your order #12345 has been shipped. Track it here: example.com", that fits comfortably within 160 characters and counts as a single SMS.

Unicode SMS: When the Limit Drops to 70 Characters

Things get interesting when you need to send messages in regional languages like Hindi, Tamil, Bengali, Marathi, Arabic, or Chinese. These characters require Unicode (UCS-2) encoding, which takes up more space per character.

With Unicode encoding, a single SMS supports only 70 characters. That is less than half of what you get with GSM-7.

Here is the catch that trips up many businesses: even a single Unicode character in an otherwise English message will force the entire message into Unicode encoding. So if you accidentally include a Hindi character or even certain emojis, your 160-character limit suddenly shrinks to 70.

If you are planning to send messages in regional languages, check out the Unicode regional language SMS guide to understand best practices and avoid unnecessary message splitting.

What Happens When You Exceed the Character Limit?

When your message exceeds the single SMS limit, the system breaks it into multiple parts known as concatenated SMS. And here is the part that surprises most people: concatenation reduces the available characters per segment because a small header is needed to reassemble the parts on the recipient's phone.

GSM-7 Concatenated SMS

Unicode Concatenated SMS

As you can see, a 161-character English message does not cost you just a tiny bit more. It actually consumes two SMS credits. At scale, this can significantly increase your bulk SMS costs if you are not careful with your message length.

Want to check your message length before sending? Use the free SMS character counter tool to see exactly how many segments your message will use.

Character Limits Across Different SMS Types

The encoding rules are the same regardless of the SMS type, but the practical implications vary depending on the use case. Let us explore how character limits affect each category.

Transactional SMS

Transactional SMS messages include alerts, order confirmations, shipping updates, appointment reminders, and account notifications. These are typically concise and rarely exceed 160 characters. However, if you are including dynamic variables like tracking links, order IDs, and customer names, the character count can creep up quickly.

Pro tip: Use URL shorteners and keep your variables concise. Instead of a full tracking URL, use shortened links to save characters.

Promotional SMS

Promotional SMS campaigns tend to be longer because they include offers, discount codes, terms, and opt-out instructions. TRAI regulations in India also require you to include sender identification and an opt-out mechanism, which eats into your character count.

A typical promotional SMS might look like this:

"FLAT 30% OFF on all electronics! Use code ELEC30 at checkout. Valid till 31st Dec. Shop now: link. Reply STOP to opt-out."

That is roughly 140 characters, right under the wire. Add a few extra words and you are looking at a two-part message.

OTP SMS

OTP SMS messages are usually the shortest of all SMS types. A standard OTP message like "Your OTP is 482937. Valid for 5 minutes. Do not share this code with anyone." comes in at about 75 characters, well within the single SMS limit.

Because OTP SMS delivery speed is critical for user experience and security, keeping these messages short ensures faster processing and delivery. Every millisecond counts when a user is waiting to verify their identity.

International SMS

When sending international SMS, the same character encoding rules apply. However, different countries and carriers may have slightly different concatenation behaviors. Some carriers display concatenated messages as a single message on the recipient's phone, while others may show them as separate messages.

If you are running international campaigns, keep your messages within the single SMS limit whenever possible to ensure consistent delivery and presentation across global networks.

Special Characters That Can Trip You Up

Not all characters in the GSM-7 character set are created equal. Some special characters actually count as two characters because they use an escape sequence. These are called extended GSM characters and include:

• Pipe symbol: |
• Curly braces: { }
• Square brackets: [ ]
• Euro sign: €
• Tilde: ~
• Caret: ^
• Backslash: \

So if you include square brackets in your message for something like [OTP: 123456], those brackets consume 4 characters instead of 2. It is a small detail, but at the margins of 160 characters, it can push your message into a second segment.

How to Optimize Your SMS Messages for Character Limits

Now that you know the rules, here are practical strategies to keep your messages within limits and save on messaging costs:

1. Keep It Short and Direct

SMS is not the medium for long paragraphs. Get to the point quickly. Every word should earn its place in the message.

2. Avoid Unnecessary Special Characters

Skip the curly braces, pipes, and other extended characters unless absolutely necessary. Use plain parentheses instead of square brackets.

3. Use URL Shorteners

Long URLs are character killers. Shorten your tracking links to save precious space, especially in promotional SMS campaigns.

4. Test Before You Send

Always preview your message and check the segment count before launching a campaign. The SMS character counter tool makes this effortless.

5. Be Careful with Copy-Paste

Copying text from word processors or websites can introduce hidden Unicode characters like smart quotes (" " instead of straight quotes " ") or em dashes. These invisible characters will switch your encoding to Unicode and slash your character limit.

6. Use DLT-Approved Templates

In India, all bulk SMS campaigns require DLT-registered templates. Design your templates with character limits in mind from the start. You can learn about the template registration process and avoid common errors by visiting the DLT template registration guide.

Why Character Limits Affect Your SMS Costs

Here is the bottom line: every SMS segment counts as one billable message. If you send a 162-character English message to 10,000 contacts, you are actually using 20,000 SMS credits instead of 10,000. That is a 100% increase in cost for just two extra characters.

For businesses running large-scale campaigns, this adds up fast. Understanding and optimizing character limits is one of the simplest ways to reduce your overall messaging spend without sacrificing communication quality.

If you are looking for transparent pricing that charges you only for delivered messages, SMSGatewayHub offers a fair pricing model designed for businesses of all sizes. Check out the SMS pricing plans to find the best fit for your needs.

Quick Reference: SMS Character Limits at a Glance

Conclusion: Master Character Limits, Master Your SMS Campaigns

Character limits might seem like a small technical detail, but they have a big impact on your messaging strategy, costs, and customer experience. To recap:

• A single English SMS supports 160 characters (GSM-7 encoding).
• A single Unicode SMS supports 70 characters.
• Concatenated messages reduce the per-segment limit to 153 (GSM-7) or 67 (Unicode) characters.
• Extended GSM characters count as two characters.
• Hidden Unicode characters from copy-paste can silently switch your encoding.

Whether you are sending transactional SMS alerts, promotional SMS offers, OTP SMS codes, or international SMS campaigns, keeping your messages concise and within the single-segment limit is the smartest move you can make.

Ready to start sending optimized, cost-effective SMS campaigns? Explore the complete range of messaging solutions at SMSGatewayHub and take control of your business communication today.