If you’re sending text and images in the same SMS, the message can contain up to 10 images and 1600 characters, as long as the entire message is under 5 MB. 

1600 characters take 4.8KB of space, which accounts for roughly 1% of the message size limit. However, please note that some special (non-GSM) characters are counted as more than one character, which affects both character count and message size. 

How Telair handles messages with non-GSM characters

If a deprecated SMS includes more than one non-GSM character, SIPSTACK will cap the limit of the SMS at 70 characters. If you want your SMS to be received without being split, please ensure that it is free of any non-GSM characters by using a third-party checker