You buy a kilo of onions. You do not put a kilo of onions in the pot — you put in what is left after peeling. Wastage is the gap, and it belongs in your cost.
Net and gross
Net qty — what the recipe uses. What ends up on the plate.
Gross qty — what leaves your inventory to produce that net.
For an ingredient with no wastage, they are the same. For one with wastage, gross is larger, and gross is what you paid for.
The maths
At 20% wastage, 100 g net needs 125 g gross. Not 120 — you divide, you do not add. The number you throw away is a share of what you bought, not of what you kept.
That difference matters. Costing 100 g of a 20%-wastage ingredient at 120 g underprices it by 4%, on every dish, forever.
Setting it
On the ingredient, in Recipe → Wastage.
It is per ingredient, not per recipe. Set 20% on onions and every recipe using onions costs at 125 g per 100 g used. Change it once, everything recosts.
That is correct: peeling loss is a property of the onion, not of the dish.
Reading it in a recipe
The recipe table shows both columns. Net qty is what you typed. Gross qty is what it actually consumes. Wastage % sits between them.
A — in the wastage column means none is set. Net and gross will be identical.
What counts
Trim, peel, bone, shell. Anything that arrives and does not reach the plate as part of that dish.
Not spoilage. Not a dropped tray. Not a portion sent back. Those are losses — real ones, worth tracking, but not this number. Wastage is the predictable, structural share you lose every single time you prep the ingredient.
If you put your spoilage rate in here, your recipes carry it forever and you will never see it as a problem.
Getting the number
Weigh it. Once.
Take a case, prep it as you normally would, weigh what you keep. That percentage is your wastage for that ingredient with that supplier.
A guess is better than zero, and weighing is better than a guess. The ingredients worth weighing are the expensive ones — a 3% error on saffron and a 3% error on onions are not the same conversation.
Zero wastage
Most ingredients have none. A bottle of oil is a bottle of oil.
Leaving it blank is correct for those. It is not a field you need to fill in everywhere — it is a field for the ingredients that lose something on the way to the pot.
Next
Recipes — where all of this arrives.