Estimate catering quantities for a full event.
Catering quantity depends on service format as much as headcount, because self-service changes portion behaviour. A plated meal delivers exactly the portion you specify, whereas a buffet needs roughly 25 percent more of everything — guests serve themselves generously, come back, and the last servings must still look presentable rather than scraped clean. Family-style shared platters land between the two. Protein is specified per head directly; sides are estimated at about 120 grams per head for each dish offered, which is why adding a fourth side raises total food noticeably even though nobody eats more.
Protein
Protein kg = attendees x g per head x format factor x (1 + contingency%) / 1000
Sides
Sides kg = attendees x 120 g x number of sides x format factor x (1 + contingency%) / 1000
Portion control disappears. Guests serve themselves generously, many return for seconds, and service dishes have to be kept looking full rather than emptied to the last spoonful. A 20 to 30 percent uplift over plated portions is standard practice.
Yes, even though appetites do not change. Each additional dish must be presented in a credible quantity and guests take a little of everything, so total food rises while consumption per head barely moves. Fewer, more generous sides is the cheaper way to cater.