Glossary
What is SMS character limit?
The SMS character limit is 160 plain characters for a single text, or 70 if it needs Unicode; longer messages are split into parts and billed per part.
People still say a text 'can only be 160 characters'. That was true of a single SMS and it's still the number that decides cost, but phones have joined longer messages for years, so in practice the limit tells you how many parts you'll pay for. With plain GSM-7 characters you get 160 in one part, then 153 per part once a text is split, so 306 characters fit in two parts and 459 in three. With Unicode it's 70 in one part and 67 per part after that.
A Glasgow dental practice with a 158-character reminder is sending one part. Add 'Thanks!' on the end and it's two.
CaptiFi Connect accepts texts up to 10 parts long. The Send SMS page counts characters and parts as you type, and the free character counter on this site does the same sum before you've even signed up.