The math depends on slice width. A 'normal' celebration slice from a 2 kg single-tier cake is about 4cm × 4cm × the cake's height. That gives 18 to 22 servings reliably.
For a buffet where the cake sits alongside three other desserts, cut the slices to 3cm wide and you'll get 24 to 26. Plate them already on small serving dishes; people take less when it's pre-portioned.
For a cake-loving crowd at a family birthday, plan for 16 slightly bigger pieces. The compliment is the second helping; some guests will quietly come back for one.
For weddings, the math shifts. A 2 kg cake at a wedding cuts as the symbolic photograph cake, with the actual serving coming from a sheet cake in the kitchen. Plan one slice per guest plus 10% — for 100 guests, that's a separate 6 kg sheet, not just the show cake.
The number depends on what you want to feel at the table. Tell us at the design call and we will quote the right kilogram count.