What's the difference between GSM-7 and UCS-2?

GSM-7 is a 7-bit alphabet covering basic Latin letters, digits, and punctuation. It fits 160 chars per SMS segment. UCS-2 is a 16-bit Unicode encoding used when your message contains characters outside GSM-7 — any emoji, curly quote, em-dash, Chinese character, etc. UCS-2 fits only 70 chars per segment, and many SMS providers charge per segment, so a single emoji can double or triple your send cost.

Why do multi-segment messages fit fewer chars than 160 × N?

Concatenated SMS reserves 7 bytes (UDH — User Data Header) per segment for reassembly metadata. So GSM-7 multi-segment is 153 chars per segment, not 160. UCS-2 multi-segment is 67 chars per segment, not 70.

Which characters force UCS-2?

Anything outside the GSM-7 default alphabet and its extension table. Common culprits: curly quotes (' ' " "), em/en dashes (– —), ellipsis (…), bullet (•), any emoji, and all non-Latin scripts. The tool highlights these so you can replace them with ASCII equivalents and stay in cheaper GSM-7.

SMS Character Counter (GSM-7, UCS-2, Segments)

SEO & Marketing· 10 tools

Free SMS character counter for marketing and transactional messages. Paste your SMS text and instantly see the encoding (GSM-7 or UCS-2 Unicode), the character count, the number of 160/70-character segments, and which characters (if any) force an upgrade to the more expensive UCS-2 encoding. Useful for SMS campaign pricing, template design, and catching hidden emoji or curly-quote characters.

SMS message

Encoding

GSM-7

Characters

septets (7-bit)

Segments

160 chars per segment

Remaining

until next segment

GSM-7: 160 chars single, 153 per multi-segment (7-byte UDH reserved). UCS-2: 70 chars single, 67 per multi-segment. Carriers bill per segment — a single emoji can turn a 1-segment message into a 3+ segment message.

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