SMS Length Calculator
Check character count, segment count, and encoding type before you send. Avoid surprise costs from multi-segment messages and UCS-2 encoding.
Check your SMS message
Special characters detected — message will use UCS-2 encoding (70 chars/segment instead of 160)
Characters
0
Encoding
GSM-7
Segments
0
Estimated Cost
£0.00
Calculation is instant and runs entirely in your browser. No data is sent to any server.
How SMS Length Works
GSM-7 Encoding
The default SMS encoding supports standard Latin letters, digits, and common punctuation. Each character uses 7 bits, giving you 160 characters per single segment. Extended characters like curly braces and the euro sign count as two characters.
UCS-2 Encoding
If your message contains any character outside the GSM-7 set (emojis, Chinese, Arabic, Cyrillic, or certain special symbols), the entire message switches to UCS-2. This uses 16 bits per character, limiting you to just 70 characters per segment.
Multi-part Messages
When a message exceeds one segment, a User Data Header (UDH) is added to each part so the recipient's phone can reassemble them in order. This header uses 7 bytes, reducing usable space to 153 characters (GSM-7) or 67 characters (UCS-2) per segment.
SMS Length Limits by Carrier
| Carrier / Provider | Max Segments | Max GSM-7 Chars | Max UCS-2 Chars |
|---|---|---|---|
| Most UK carriers | 10 | 1,530 | 670 |
| Vodafone UK | 10 | 1,530 | 670 |
| AT&T (US) | 10 | 1,530 | 670 |
| T-Mobile (US) | 6 | 918 | 402 |
| Twilio / API providers | 10 | 1,530 | 670 |
| LimeCall Business Texting | 10 | 1,530 | 670 |
Tips to Keep SMS Costs Down
Avoid emojis in transactional SMS
A single emoji forces UCS-2 encoding, cutting your character limit from 160 to 70. Remove emojis to keep costs down on high-volume campaigns.
Use a URL shortener
Long URLs eat up characters fast. Use a branded short link (e.g. link.yourbrand.com/offer) to save 30-50 characters per message.
Test every message with this tool
Paste your final SMS copy into this calculator before sending. A single curly quote or accented character can double your segment count.
Keep messages under 160 characters
Single-segment messages are cheapest and arrive fastest. Write concise copy and trim filler words to stay within one segment.
Watch for hidden Unicode characters
Copying text from Word, Google Docs, or email clients can introduce smart quotes, em dashes, and non-breaking spaces that trigger UCS-2 encoding.
Frequently asked questions
How many characters in an SMS? +
A single SMS message can contain up to 160 characters when using the GSM-7 encoding (standard Latin letters, numbers, and common symbols). If your message contains special characters, emojis, or non-Latin scripts, it switches to UCS-2 encoding which allows only 70 characters per message segment.
What is an SMS segment? +
An SMS segment is a single unit of a text message. If your message exceeds the character limit (160 for GSM-7 or 70 for UCS-2), it is split into multiple segments. Each segment is sent and billed separately. Multi-part messages use a User Data Header (UDH) which reduces the usable characters to 153 per segment for GSM-7 or 67 per segment for UCS-2.
Why do emojis use more characters in SMS? +
Emojis are not part of the GSM-7 character set, so including even one emoji forces the entire message to use UCS-2 encoding. UCS-2 uses 16 bits per character instead of 7 bits, which reduces the maximum characters per segment from 160 to 70. This means a message with a single emoji can cost twice as much to send as the same text without it.
What is the difference between GSM-7 and UCS-2 encoding? +
GSM-7 is the default SMS encoding that supports 128 standard characters (Latin letters, digits, and common punctuation) using 7 bits per character, allowing 160 characters per segment. UCS-2 is a Unicode encoding that supports virtually all world scripts, emojis, and special symbols using 16 bits per character, but limits each segment to 70 characters. Your message encoding is determined automatically based on the characters used.
How much does an SMS cost? +
SMS pricing depends on the carrier, destination country, and number of segments. In the UK, a single segment typically costs between 3p and 5p. A 200-character GSM-7 message would use 2 segments and therefore cost double. With LimeCall business texting, SMS starts from as low as 3.5p per segment with volume discounts available.
Can I send long SMS messages? +
Yes, you can send SMS messages longer than 160 characters. The message is automatically split into multiple segments by the carrier and reassembled on the recipient's device. Most carriers support up to 10 segments (1,530 GSM-7 characters or 670 UCS-2 characters) in a single concatenated message. Each segment is billed individually, so longer messages cost more to send.
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