Splitting a bill has two failure modes: the vanishing cent, and the person who "just had a salad." This calculator kills both — exact-cent allocation in even mode, and weighted shares when orders genuinely diverge.
Even mode and the honest cent
$127.40 plus 18% tip is $150.33 among four people: three pay $37.58, one pays $37.59 — and the calculator says which, because 4 × $37.58 is a cent short and someone must absorb it. Small stakes, but exactness is the whole point of using a calculator.
Weighted mode: fairness with dignity
Instead of itemizing every fry, assign weights: 1 for a normal share, 2 for the double-main friend, 0.5 for the salad. Each pays total × weight ÷ weight-sum, with leftover cents distributed by largest remainder — the same method parliaments use to allocate seats, because it's provably the fairest rounding.
Tip and tax ride along
The tip percentage applies to the whole bill before splitting, so both modes stay proportional — the convention that keeps servers whole and math simple. (Tip-focused math with per-person amounts and service-quality guidance lives in the tip calculator.)
The social calculus
Behavioral studies of group dining find people order slightly more under an even split — the cost is shared but the burger is yours. Even splits stay socially cheapest for similar orders; weights fix the incentive when someone's wine flight enters the picture. For dividing anything else by ratio — rent by room size, chores by hours — the ratio calculator generalizes the trick.
All shares sum to the exact total, verified to the cent.