"Catering quantities" covers more than just food - a fully planned event needs four separate calculations: how much food, how much to drink, how many staff, and how many disposables. Get any one of these wrong and the event feels it, whether that's running out of chafing dishes or being short a bartender during the dinner rush.
Start with guest count, service style, and meal type. Plated dinners use standard portions; buffets run roughly 10% higher because of self-serve overage; cocktail/passed events use much smaller per-category amounts spread across more items. Add a buffer - commonly 15% for events under 200 guests, tapering to around 11% for very large events.
Plan on roughly 2 non-alcoholic servings and 1 alcoholic drink per person per hour of event, adjusted for whether a bar is even present. Ice needs are separate from drink quantities: about 1lb per person if it's only cooling drinks, closer to 1.5-2lb per person if it's also keeping food cold in tubs or coolers.
Buffet service typically needs one server per 20-25 guests; plated/seated service is more labor-intensive at roughly one server per 12-16 guests. Add a bartender per 50-75 guests if there's a bar, and kitchen/prep staff at a similar ratio - though that last one varies the most by menu complexity, so treat it as a starting point rather than a hard rule.
Plates: 1 per person plus about a 10% buffer. Napkins: roughly 2 per person. Cutlery: 1 set per person. Cups: 1.5-2 per person to account for refills. For buffet service, budget one full-size chafing pan per 25-30 guests per hot dish (or two half-size pans covering roughly the same range).
Catering Calc runs the food-quantity math free in your browser below, and the mobile app adds the other three (beverages, staffing, disposables) plus saved event templates so you're not re-entering the same guest count four times.
Plug in your guest count and get exact numbers in seconds.