SMS Character Limit: 160, 70 and Why Messages Split

Why 160?

A single text message holds up to 160 characters when it is written with the standard GSM-7 alphabet. The limit comes from the original design of SMS, which fitted a message into a fixed-size packet. GSM-7 uses 7 bits for each character, and 160 characters of 7 bits fill the packet.

The alphabet covers the basic Latin letters, digits, common punctuation and some accented letters. It is not the same as ASCII, and some of the characters people expect to find in it are missing.

The switch to 70

Any character outside the GSM-7 set forces the whole message into a different encoding called UCS-2, which uses 16 bits per character. A message in UCS-2 holds only 70 characters in a single segment. The change affects the entire message, not only the one unusual character.

Common triggers are emoji, Chinese, Japanese and Korean characters, many accented letters outside the GSM set and typographic quotation marks. A message written in Word and pasted into a sending tool often contains curly quotes, which silently reduce the limit from 160 to 70.

Segments and how they are counted

A message longer than the limit is split into several segments and put back together by the phone. Each segment carries a small header of 7 characters worth of space that tells the phone how to assemble them, so the room for text per segment falls to 153 characters in GSM-7 and 67 in UCS-2.

Two segments therefore hold 306 characters in GSM-7 and 134 in UCS-2. Providers often count and bill each segment as a separate message, so a message that is just over the limit can double the cost. Check the rules of your provider.

Extension characters

A small group of characters in the GSM-7 set, including the euro sign and square and curly brackets, belongs to an extension table. Each of them takes two places in the message instead of one. A message with several such characters can reach the limit before the character count suggests it should.

A plain character counter, including this one, counts each of these symbols as one, so for messages that use them leave a few characters of margin.

How to check a message

Paste the text into the counter and select the custom limit. Enter 160 for a message that uses only plain characters and read the bar. If the text contains an emoji, a curly quote or a non-Latin letter, use 70 instead, and when the text is longer than one segment, plan on 153 or 67 per segment.

This counter shows characters, not segments, so do the segment arithmetic yourself: divide the count by 153 for GSM-7 or by 67 for UCS-2 and round up. For billing questions, use the tool of your SMS provider, which applies its own rules.

Writing short, clear messages

A text message works best when it is short. Put the key information first, say who you are, and end with one clear action such as a link or a reply word. Avoid emoji in messages where cost or reach matters, since one emoji can cut the capacity of a segment by more than half.

Replace curly quotes and long dashes with plain ones if you need to stay inside the GSM-7 alphabet. Many sending platforms show a warning when a message switches to UCS-2, and some can replace the characters for you.

A worked example

Take a reminder of 150 characters in plain text. It fits one segment, since the limit is 160. Add a single emoji at the end and the whole message becomes UCS-2, where one segment holds 70 characters. The 151 characters now need three segments of 67, 67 and 17 characters, which can triple the cost.

Remove the emoji and the message returns to one segment. This is why many senders keep a plain text version for important notices and test the final text before a mass send.

Why SMS limits still matter

It may seem odd that a limit from the 1990s still shapes messages today. SMS remains in use because it works on every phone without an app or an internet connection, and it is the channel for one-time codes, delivery notices and appointment reminders that must arrive reliably.

For those uses, short and plain is a strength. A message that fits in one segment is cheaper, arrives as one piece and is easier to read on a small screen.

Other messaging apps

Messaging apps such as WhatsApp, Telegram and iMessage do not use SMS segments, and their limits are much higher. The 160-character rule applies to classic SMS only, and to systems that send through it, such as many bank codes, delivery notices and appointment reminders.

If your audience uses an app, you rarely need to count. If you reach people by SMS, count every message, because the limit decides how much it costs and whether it arrives as one message or several.

A quick checklist

• Plain text: 160 characters in one segment, 153 per segment when split.
• With an emoji or non-Latin text: 70 in one segment, 67 when split.
• Check for curly quotes and special symbols.
• Leave a margin for extension characters.
• Confirm segment counts and costs with your provider.

Limits and billing rules can differ between carriers and countries, so treat the figures here as the standard and confirm them for your route.