Here are some questions to ask yourself to assist in ordering the right quantity of ice.
How long is your bar open for?
What are you serving at the bar?
Will there be cocktails? Iced water? Or just for chilling?
A good rule of thumb based on a 6 hour bar service serving water, pop and highballs.
Chilling: 1.5 pounds per person
Chilling & Serving: 2.5 pounds per person
Chilling & Serving (Hot Summer Outdoor Event): 3 pounds per person