An SMS is limited to 160 characters when using standard GSM-7 encoding (the most common encoding for text messages). This includes spaces, punctuation, and special characters. If your message contains characters not supported by GSM-7 (e.g., certain emojis or non-Latin characters), it will be sent using Unicode encoding (UCS-2). In this case, the character limit is reduced to 70 characters per SMS. For longer messages, SMS uses a feature called "concatenation" to split the text into multiple parts. Each part reserves characters for linking, reducing the effective limit to 153 characters per part for GSM-7 or 67 characters per part for UCS-2. For example: • A 300-character message in GSM-7 will be split into 2 parts of 153 characters and 1 part of 94 characters. • A 300-character message in UCS-2 will require 5 parts of 67 characters each. The price for sending SMS is calculated per part, so longer messages may incur higher costs.