SMS gives you 160 characters only when your message uses the basic GSM character set. Add an emoji, curly quote, or many non-English letters, and that limit can drop to 70 characters because the message switches to Unicode [source: Twilio].
TLDR: A plain SMS can fit 160 characters, like “Your code is 482913.” But a Unicode SMS usually fits only 70 characters, such as “Your code is 482913 😊.” That tiny emoji can turn one neat message into two billable parts. If a shop sends 10,000 promo texts and 12% become two-part messages, that means 1,200 extra SMS segments to pay for.
The simple version
SMS is old. Very old. It was built for short text. Not stickers. Not GIFs. Not dramatic emoji chains.
The magic number is 160. That is the classic SMS limit. But it only applies when your message uses GSM-7. That is a compact character set made for basic letters, numbers, and symbols.
Unicode is bigger. It supports almost every writing system. It also supports emoji. Great for humans. Less great for SMS length.
So the real rule is this:
- GSM-7 message: up to 160 characters.
- Unicode message: up to 70 characters.
- Long GSM-7 message: split into parts of 153 characters.
- Long Unicode message: split into parts of 67 characters.
Annoying? Yes. Random? Not quite.
Why 160 characters?
SMS was designed to squeeze text into a small data space. Engineers had to be clever. With GSM-7 encoding, each character uses 7 bits. That lets one SMS carry 160 characters.
Think of it like packing socks into a tiny drawer. Thin socks fit. Big winter socks do not. GSM-7 is the thin sock. Unicode is the big woolly sock with snowflakes on it.
GSM-7 covers many common characters, such as:
- English letters: A to Z and a to z
- Numbers: 0 to 9
- Basic punctuation: ., !, ?, ,
- Some currency symbols, like $ and £
If your message sticks to these, you get the full 160. Nice and tidy.
What triggers Unicode?
This is where people get caught. One tiny character can flip the whole SMS into Unicode mode.
Common Unicode triggers include:
- Emoji: 😊 🚀 ❤️
- Smart quotes: “like this” instead of “like this”
- Non-Latin scripts: Arabic, Chinese, Japanese, Hindi, Cyrillic, and more
- Accented characters not supported by GSM-7
- Fancy symbols: ™, —, •, ✓
It drives me a little nuts that a single curly apostrophe can quietly change the whole message. You write a clean 145-character text. Then your phone or editor swaps a straight quote for a smart one. Boom. Now you may be over the Unicode limit.
Wait, what happens after the limit?
Your message does not just explode. It gets split.
This is called concatenated SMS. That just means “glued together SMS.” Your carrier breaks the long text into smaller chunks. The phone then puts them back together for the reader.
Most users never notice. They see one long message. But billing systems often count each chunk as a separate SMS segment.
Here is the sneaky part:
- A single GSM-7 SMS holds 160 characters.
- A multi-part GSM-7 SMS holds 153 characters per part.
- A single Unicode SMS holds 70 characters.
- A multi-part Unicode SMS holds 67 characters per part.
Why the smaller number? Because each part needs a small header. That header tells the phone, “Hey, I am part 2 of 3.” Useful, but it steals space.
A quick example
Message one:
Your appointment is tomorrow at 3 PM. Reply YES to confirm.
This uses GSM-7. It is short. It sends as one SMS.
Message two:
Your appointment is tomorrow at 3 PM 😊 Reply YES to confirm.
That emoji changes the encoding. Now the message is Unicode. It may still fit in one part, but the ceiling is much lower.
Now try this campaign text:
Flash sale today only! Get 25% off all jackets, shoes, and bags. Use code SAVE25 at checkout. Offer ends at midnight. Don’t miss it 😊
Looks harmless. But it has a smart apostrophe in Don’t and an emoji. That can push it into Unicode. If it goes over 70 characters, it becomes a multi-part Unicode message.
Why marketers should care
If you send one text to a friend, this is trivia. If you send 50,000 texts to customers, this is money.
Let’s say your SMS provider charges per segment. You plan a campaign of 50,000 messages. You expect each message to be one segment. Then someone adds an emoji and a long sentence. Now each message becomes two Unicode segments.
Your send volume did not feel like it changed. But your bill did. It doubled.
That is the part nobody enjoys explaining to finance.
Characters that cause sneaky trouble
Some characters look normal. They are not always normal in SMS land.
Watch out for these:
- Curly quotes: “ ” ‘ ’
- Long dash: —
- Bullet: •
- Check mark: ✓
- Emoji: any of them
- Trademark symbols: ™ and ®
Also, some GSM-7 characters are extra needy. They count as two characters because they need an escape code.
These include:
- { and }
- [ and ]
- ^
- ~
- \
- |
- €
So yes, even a short message can be sneakier than it looks.
How to keep texts short and cheap
Use these simple habits:
- Use plain text. Skip emoji in high-volume campaigns.
- Use straight quotes. Type ” and ‘ instead of curly versions.
- Shorten links. Long URLs eat space fast.
- Cut filler words. “Sale ends tonight” beats “We wanted to let you know our sale ends tonight.”
- Test before sending. Use a character counter that detects GSM-7 vs Unicode.
- Check segment count. Do not stop at character count.
Honestly, it feels like overkill until you save thousands of segments in one campaign. Then everyone suddenly loves the boring character counter.
When Unicode is worth it
Unicode is not bad. It is just heavier.
You need Unicode when your audience uses languages outside GSM-7. If you send messages in Arabic, Chinese, Japanese, Korean, Hindi, Ukrainian, or many other languages, Unicode is the right choice.
You may also want emoji for brand voice. A pizza shop can send “Free slice 🍕 today” and get attention. That emoji may be worth the extra cost if it boosts clicks or visits.
The point is not “never use Unicode.” The point is know when you are using it.
SMS vs MMS vs messaging apps
SMS is plain text. It has strict size rules.
MMS can include images, longer text, and media. It often costs more. It also behaves differently across carriers and devices.
Messaging apps like WhatsApp, Messenger, and iMessage are not SMS. They use internet data. Their limits are different. But they also require the user to be on that platform.
For alerts, codes, reminders, and quick promos, SMS is still hard to beat. It is simple. It is direct. People read it fast.
The best rule of thumb
Write your SMS like every character has a tiny price tag. Because sometimes it does.
If your message is plain, aim for 160 characters or less. If it has emoji or non-GSM characters, aim for 70 characters or less. For longer campaigns, check the number of SMS segments before you hit send.
One emoji can be cute. One hidden Unicode character can be expensive. That is the whole SMS character limit story in one slightly irritating nutshell.
