The 15-person threshold
The cleanest way to divide food costs among a big group: one person takes the itemized receipt, assigns each dish to whoever ordered it, and sends everyone a request for their exact share—tax and tip included. Don’t split evenly, and don’t hand the server a stack of cards. The rest of this guide is the research on why every other method breaks at this size, and the playbook for running that system without becoming the table’s unpaid accountant.
Something changes when a group crosses 15 people. A birthday dinner for 8 is manageable. A wedding party of 12 is complex but solvable. But at 15, 20, or 30 people, the bill-splitting problem becomes qualitatively different. Not just harder—different in kind.
The dollars climb just as fast as the headcount. What a group restaurant bill actually costs shows how far into the high end large tables land, which is exactly where an even split goes most wrong.
The coordination cost is what climbs fastest. For a small group it’s trivial—four people can glance at each other and know who’s doing what. But the number of two-way connections in a group grows combinatorially, far faster than the headcount. A group of 4 has 6 possible two-way communication links. A group of 20 has 190. The cognitive load of tracking who ordered what, who already paid, and who’s waiting for someone else becomes overwhelming.
The formula is n(n-1)/2, where n is the number of people. At 15 people, you have 105 potential coordination pairs. At 25 people, 300. Not every pair actually needs to talk—but every link is a place for a crossed wire, a duplicate payment, or an “I thought you had it.” That’s why the fix that runs through this whole guide is structural: appoint one collector, and a 20-person settlement collapses from 190 potential conversations into 19 direct ones.