Event ROI refers to the return on investment of holding an event. It is calculated as the benefit of achieving the event objective divided by the total event costs. To maximize event ROI, organizers should first set clear objectives for why the event is being held and how it will create value. Second, they should map out specific actions participants should take. Third, organizers need to measure and evaluate whether the objectives and actions were achieved, such as through sales or surveys. Finally, they should learn from the event to improve ROI for future events.