The max amount of characters that can be sent out as one Text Message will greatly depend on the type of characters used in your Text Message. GSM-7 is the standard character encoding used when sending out Text Messages. Most commonly used characters can be encoded into this format, which would allow for a message to be up to 160 characters before it is broken up into multiple text messages.
However, if your message includes a Unicode Character, which cannot be encoded using the standard GSM-7, then your entire message will be covered using ucs-2 encoding, which will only allow a max of 70 characters per text message.
Each text message that is sent to a wireless handset has a limitation of a max size of 140 bytes per message. Using the GSM-7 standard encoding, the majority of characters used take up a size of 7-bits.
Since 8 bits = 1 byte, when using GSM-7 encoded characters in your message - you can have up to 160 characters (8 bits * 140 bytes = 1,120 / 7 bits per character = 160 characters) before your message is broken up into several messages.
If your message includes a non-GSM-7 character, your entire message will be encoded into UCS-2. UCS-2 characters will take up either 2 or 4 bytes. This means, if your message is encoded into UCS-2 then the max amount of characters you can fit into one message is 70 characters (8 bits * 140 bytes = 1,120 / 16 bits per character = 70 characters).
This Page, SMS Character Checker, is a useful tool when checking to see if your current message will be broken up into multiple messages.
When we receive a request to send out a text message with over 160 characters, then your messages must be split up in order to be sent to the wireless subscriber.
Ytel bills per message and NOT per request. For example, if you send out a text message that has 250 characters, then you will be charged for two text messages since your message will be broken up into two messages. In this example, if you are paying $0.02 per SMS, then you would be charged $0.04 for the SMS ($0.02 * 2 = $0.04).
Keep in mind that this example is assuming all of the characters in your message can be encoded into GSM-7, otherwise your character limit per message can drop down to 70 characters per message if sending any Unicode Characters (See here for more details on Understanding Unicode
MMS messages have restrictions as well. For long code phone numbers, all image files need to be kept under 1 MB in size. For Tollfree numbers, that file restriction drops down to 500 KB.
Not all text editors will use GSM-7 encoding when creating your Message. It is important to use an SMS character checker to verify that none of your characters are being encoded into UCS-2 when you copy the text message body from a document editor such as Microsoft Word or Google Docs over to your SMS program.
Updated 11 months ago