A method for adjusting fuel injection quantities in an internal combustion engine configured to operate multi-pulse fuel injections in a cylinder of the engine includes monitoring in-cylinder pressure, determining a burnt fuel mass for main combustion based upon the in-cylinder pressure, determining a burnt fuel mass for post combustion based upon the in-cylinder pressure, determining a main fuel quantity offset based upon the burnt fuel mass for main combustion, determining a post fuel quantity offset based upon the burnt fuel mass for post combustion, and controlling fuel injections into the cylinder based upon the main fuel quantity offset and the post fuel quantity offset.