A method and system for generating a reply message limited to a maximum number of characters based on a dynamic variation of an original message length. A messaging client receives the original message and delivers the original message text for presentation to a user. If the user opts to reply to the original message, the messaging client generates the reply message by including the user's reply message text and only so much of the original message text as will fit in a remaining capacity of the reply message. The method and system is particularly useful in a Short Message Service (SMS) messaging system, but may be useful in other systems as well.