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. Trim loss is the gap, and it belongs in your cost.
In the app the field is labelled Wastage. It is the planned loss. The unplanned one — spoiled, expired, dropped — is Waste, and is declared separately.
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 a product with no trim loss, they are the same. With trim loss, gross is larger, and gross is what you paid for.
The maths
At 20%, 100 g net needs 125 g gross. Not 120 — you divide, you do not add. The share you throw away is a share of what you bought, not of what you kept.
That difference matters. Costing 100 g of a 20% product at 120 g underprices it by 4%, on every dish, forever.
Setting it
On the product, under Recipe → Wastage.
It is per product, 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 Net qty, Wastage % and Gross qty. A — in the wastage column means none is set; net and gross are identical.
What counts
Trim, peel, bone, shell. Anything that arrives and does not reach the plate every single time you prep it.
Not spoilage. Not a dropped tray. Not a portion sent back. Those are real losses — declare them as waste. Put your spoilage rate in here and your recipes carry it forever; 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.
A guess is better than zero, and weighing is better than a guess. Weigh the expensive ones first — 3% on saffron and 3% on onions are not the same conversation.
Fish, meat and seafood usually arrive already worked; a fillet has no peel.
Zero
Most products have none. A bottle of oil is a bottle of oil. Leaving it blank is correct.
Next
Waste — the loss nobody planned.