Theoretical vs actual: the gap that finds your profit leak

The percentage says something is happening. The variance says where. One subtraction turns your weekly food cost from a mood into a map.

Every operation has two food costs. There is the one your menu promised: take what you actually sold this week, cost each dish at its recipe yield and current ingredient prices, and add it up. That is your theoretical food cost, the cost of a kitchen that made no mistakes. Then there is the one your kitchen delivered, the actual cost, straight off purchases and stock counts. Almost nobody calculates the first one. Which is a shame, because the difference between the two is the most honest number in the building.

The two numbers, defined

Theoretical food cost is what the week should have cost: your real sales mix, priced at recipe cards. It assumes perfect portions, zero waste, no comps, no theft, no drift. It is a fiction, but a useful one, because it is the standard the kitchen was aiming at.

Actual food cost is what the week did cost: opening stock plus purchases minus closing stock. It contains everything that really happened, including everything you would rather it didn't.

Subtract one from the other and you get the variance. That gap has a short list of possible causes: waste, over-portioning, comps and staff meals that never got recorded, prep errors, recipe drift, and loss. Every euro in the gap belongs to one of those. None of them belongs on a price increase.

A week in numbers

Say your restaurant sold €10,000 this week. Costing the actual sales mix at recipe yields, the theoretical food cost comes to 30%, which is €3,000. The stock count says the kitchen actually consumed €3,300, which is 33%. The variance is €300.

Here is what that €300 is not: it is not a supplier problem, because supplier prices are inside both numbers. It is not a menu-pricing problem, because prices are inside both numbers too. It is purely operational, which means it is purely fixable, and it is worth about €15,600 a year at this pace. Left inside a single blended percentage, it is invisible.

How big is too big?

• Under 2% of sales: healthy. This is the ordinary friction of a working kitchen. Keep the routine that got you here.
• 2% to 5%: watch it. Pick the three highest-value ingredients, weigh portions on the line for a week, and check that comps and staff meals actually get keyed in.
• Over 5%: investigate now, not at month end. At this size the gap is usually one specific thing: a broken portion spec, an unrecorded waste stream, or someone helping themselves.

The percentage says "something is happening." The variance says "where."

Making it a habit

This is a weekly discipline, not a project. You need three things in place: recipe cards that are actually costed at current prices, a sales-mix report out of the POS, and a stock count you trust. With those, the calculation is an hour on a Monday. If your food cost moves and you don't know why, this is the subtraction that answers the question before the blame starts.

Most operators skip it because the theoretical side feels like homework. It is homework once. After the recipe cards are costed, the number updates itself with every price change, and every Monday you get the one report that separates "the market got more expensive" from "the kitchen got looser." Those are different problems, with different fixes, and only the variance can tell them apart.