Your prep plan talks in recipe amounts. Your supplier talks in cases, bags, bottles and eaches. A shopping list you can use gets you from one to the other, and nobody sells you a third of a sealed case.

Start with the menu and guest count

Scale each dish to the event, sub-recipes included, plus whatever you cook over the guarantee on purpose. Write that overage down as overage. Bury it in a padded guest count and you can’t line the quote up against the prep plan later.

Combine the same ingredient

If onions go into the soup, the salad and the sauce, add them up before you turn them into cases. Make sure it really is the same product. Red, yellow, peeled and frozen diced onion are not one line just because they all say onion.

Convert the total into the supplier unit

Suppose the event requires 132 lb of chicken and the selected supplier sells 40 lb cases:

Packs needed = required quantity ÷ quantity per pack
132 lb ÷ 40 lb = 3.3 cases

You cannot order 3.3 sealed cases. Round up to four, unless the supplier will break a case for you or you choose to split the order with another product you’ve approved.

4 cases × 40 lb = 160 lb purchased
160 lb − 132 lb = 28 lb above the planned need

Those 28 lb are worth knowing about. They might cover trim and slack you already planned for somewhere else, go on the shelf on purpose, or tell you a different pack size fits better. Don’t hide them by changing the recipe need to 160 lb.

Treat on-hand stock as evidence

Only take stock off the buy when you’d bet this order on the number. Note when it was counted and what came in, got used or got adjusted since. If the count is old, say so, and either buy the full need or go count again.

Group the result by supplier

A buy list you can work from shows:

  • Ingredient and approved product.
  • Total kitchen need in a useful unit.
  • Supplier pack description.
  • Whole packs to order.
  • Quantity the packs provide.
  • Any known on-hand deduction.
  • Need-by date and event context.

The supplier gets an order it can fill. The kitchen keeps the amount the recipes will actually use. You need both numbers, so don’t squash them into one.