The automatic gratuities amount Carnival currently applies is $13.99 per person per day to standard rooms and $15.99 per person per day for suite staterooms.  This amount is shared among dining, bra, and culinary services staff, stateroom attendants, and other hotel services team members working behind the scenes.  You may:

• add gratuities to your booking and prepay them at any time up until final payment
• wait until you board the ship and he gratuities will be applied to your onboard account

For more information on gratuities click here and scroll to Service Gratuities.