How Many Characters Are in 1 SMS? GSM-7 vs Unicode
One SMS can quietly become two, and cost twice as much, all from a single emoji. Here's how GSM-7 and Unicode encoding work, and how to stay in one segment.
You type a short message, sure it's one SMS, but the bill says two. The culprit is almost always the same: encoding. Once you understand GSM-7 and UCS-2, you can keep every message short, cheap, and in one piece.
160 or 70? It depends on the encoding
SMS isn't unlimited free text. Each message is encoded with one of two schemes, and that scheme decides how many characters fit in a single SMS.
| Encoding | 1 SMS | Per segment (long message) | Used for |
|---|---|---|---|
| GSM-7 | 160 characters | 153 characters | Letters, numbers, and common punctuation |
| Unicode (UCS-2) | 70 characters | 67 characters | Emoji, non-Latin scripts, special characters |
The moment one character falls outside the GSM-7 set, the encoder shifts the entire message to Unicode (UCS-2), and the limit drops from 160 to 70 in one go.
What quietly triggers Unicode
- Any emoji, even a single one is enough.
- Smart quotes (' ' " ") and long dashes (, –) that sneak in when you copy from Word or Notes.
- Accented letters like é, ñ, ü, or ç.
- Arrows and special symbols (→, ★, ✓) and non-Latin scripts (Arabic, Chinese).
Add one emoji to a 150-character message and it becomes Unicode (70-char limit). Those 150 characters now need three segments, so you pay for three SMS to send one message.
Characters that are safe in GSM-7
As long as you stick to these, your message stays on GSM-7 and fits 160 characters:
- Letters A–Z and a–z, and digits 0–9.
- Space and common punctuation: ., ? ! : ; ' " ( ) / + - * = % & @ #
- Note: a few symbols like [ ] { } \ ~ ^ | and € are "GSM extended" and count as 2 characters each.
Long messages get split, and each one is billed
Cross the limit and the message splits into several SMS, then gets stitched back together on the recipient's phone. Each part is sent and billed separately. And because each part reserves room for the stitching info (a UDH header), the limit drops to about 153 characters (GSM-7) or 67 (Unicode) per part.
What Zenziva supports
Zenziva SMS uses GSM-7: letters, numbers, spaces, and common punctuation, with no emoji or non-GSM characters. A single SMS holds 160 characters; if it's longer, Zenziva concatenates up to 4 SMS (around 153 characters per part) and bills per SMS. Sticking to GSM-7 is deliberate, since it keeps delivery reliable and the cost down.
Tips to keep an SMS to one segment
- Type directly in the message field; don't paste from Word, that's the main source of smart quotes and Unicode dashes.
- Skip emoji. For a warm tone, lean on word choice, not icons.
- Shorten links and trim filler to stay under 160.
- Use a brand-name Sender ID instead of writing your brand inside the body, it saves characters and adds trust.
- GSM-7 fits 160 characters; Unicode only 70.
- One emoji or special character flips the whole message to Unicode.
- Messages over the limit split into several SMS, and each segment is billed.
- Zenziva uses GSM-7 (no emoji) for reliable, cost-efficient messages.
Want to calculate the per-message cost for your volume? Visit the pricing page, or sign up and start sending SMS Masking with your brand-name Sender ID today.
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