How Much Cake for 120 People?

Sheet cakes serve party-size 2×2 inch slices: about 24 from a quarter sheet, 48 from a half, 96 from a full sheet. A 9-inch round serves about 12.

If you're also serving other desserts, a cake sized for 75% of guests never runs out.

Adjusting for your crowd: kids eat about two-thirds of adult portions; knock 25% off any single item when several mains share the table; add 25% for teenagers and big appetites. When in doubt, round up on the cheap items (buns, chips, ice) and stay exact on the expensive ones.