A seating chart is two rules and a lot of judgment. Rule one: people who come together sit together. Rule two: some pairs must never share a table. Everything else is taste.
Households and couples always. Close friend groups, almost always - a table of eight college friends has a better night than eight pairs split across four tables. The exception: a group larger than one table. Split them into two neighbouring tables rather than scattering them across the room.
Make the list early and make it explicit: the divorced parents, the siblings not speaking, the two colleagues mid-dispute. "Away from each other" usually means different tables in the same room, not opposite ends of the building - but if it means opposite ends, only you know that, so say it out loud to whoever seats them.
A dedicated kids' table works from about age seven up. Younger children sit with parents. Teenagers strongly prefer their own table to the "young end" of an adult table.
Singles, plus-ones who know nobody, the cousin's new partner. Seat them together with one social anchor - the friend who talks to anyone - and it becomes the best table in the room. Scatter them as fillers and it is the worst.
A party of 14 cannot fit a table of 10; two keep-apart parties cannot both sit near the head table if there is only one table near it. Decide which rule bends before you start dragging. The tool warns you either way - splits and rule breaks are shown, never hidden.
Set your keep-apart pairs and auto-seat the rest in the free maker.
Try the rules