The length of your message is calculated based on the types of characters it contains. SMS messages use two primary character encodings: GSM 7-bit and Unicode.
GSM 7-bit encoding is commonly used for cell phone messaging and primarily includes alphabet letters and numbers. Each 7-bit character counts as one character, except for special characters (^, €, {, }, [, ], ~, \) which count as two characters each. A GSM 7-bit encoded SMS message can be up to 160 characters long. Here are some other one-character GSM 7-bit encoded letters:
Unicode supports a wider range of characters compared to GSM 7-bit. This includes emojis, special symbols, and characters from various languages. An SMS containing Unicode characters has a maximum length of 70 characters.