The iPhone has included a text messaging feature all the way back to the original model, but it took up until the release of iOS 4 to add in the ability to see how many characters your messages include. The character count feature is, however, disabled by default.
iOS 4’s SMS Character Count feature
Here’s how to enable the Character Count feature for text messages in iOS 4:
Character Countto turn the feature on
Character count in the Messages app
The Character Count display turns on somewhere between 25 and 30 characters and shows how close you are to hitting the traditional 160 character SMS limit. Going over the limit doesn’t mean your text message won’t be delivered; Instead, it splits your text across multiple messages.
For users that budget their text messages, this is a great way to make sure you don’t jump up over the 160 character limit and end up with more SMS charges than you anticipated.