Party Food and Drink Calculator

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Rules of thumb from catering practice, rounded up — parties run out of ice and cups long before they run out of anything else.

A two-hour barbecue and an eight-hour barbecue get the same food

The party length looks like it feeds everything. It does not. Of the four meal modes, party length enters the food total in exactly 1 of them — the appetiser mode, where the bites formula uses it. In sit-down meal, barbecue, dessert mode the food is a function of the guest count alone.

For thirty guests, going from two hours to eight multiplies the drinks by 3×, from 90 servings to 270, and multiplies the food by 1×. Same burgers, same buns, same sides, same charcoal. That is defensible — people eat one dinner however long they stay — but it is worth knowing before you plan an all-day event off the food column.

The two time models disagree about when a party slows down

Both the appetiser and the drinks formula model people tapering off, and they put the elbow in different places and make it a different size. Appetites are assumed to drop after hour 2 (6 pieces an hour down to 4, a 33% cut); thirst after hour 1 (2 drinks down to 1, a 50% cut).

Neither tapers twice. After its one step down each rate holds flat forever, so hour eight is modelled exactly like hour three and the averages above only drift toward 4 and 1 without ever arriving. This is not a bug so much as two rules of thumb that were never checked against each other.

Half the round-ups never round anything

Every quantity is wrapped in a round-up, which sounds like it is protecting you everywhere. Sweeping guest counts 1 to 500, 8 of the 16 quantity lines never round at all, because their multiplier is a whole number and so is the guest count.

Hot dogs at one each, cups at three, napkins at four — the ceiling is ceremony. The lines that genuinely round are the fractional ones, and a half multiplier like burgers or bread rounds for exactly the odd guest counts and no others.

One line is not rounding but quantising. Charcoal is 5 pounds per 15 guests, rounded up to a whole step, so it is only ever exact on a multiple of 15. At 16 guests it asks for 10 pounds to cover 5.33 pounds of need — 88% over, the worst case for any party of ten or more. That is right for a thing sold in bags and wrong to read as a measurement.

Children are discounted on three lines out of eleven

The kids field reduces Burgers, Buns, Main protein. It does not touch the other 8, which are flat in it across its whole range.

So a party of twenty where nineteen are children still orders twenty hot dogs and thirty dessert bites, while the burger count falls from 30 to 21. If your party is mostly children, dessert is the line to override by hand — which is, in fairness, the line children are least likely to under-eat.