What this calculation means
Proportional waste costing assigns part of a known purchase cost to a stated discarded share. It assumes cost is distributed proportionally across that purchase.
This is not a log-based sum of differently priced discarded items and does not estimate lost sales or labor.
How to use this calculator
Enter the purchase cost and the matching waste percentage. Use a percentage that belongs to that same item and cost boundary.
Formula and variables
Assigned waste cost = Purchase cost × Waste percentage ÷ 100
- Purchase costUSD
- Total cost before waste adjustment.
- Waste percentage%
- Unusable proportion, such as 15 for 15%.
Dollar amounts display to cents, with exact half-cent values rounded away from zero; intermediate calculations keep full precision.
Understand your result
The main result assigns purchase cost proportionally to the entered discarded share. Details separately show the purchase cost left with the retained food. Neither amount is lost revenue or guaranteed avoidable expense.
Worked example
15% of an $18 purchase is discarded.
Purchase cost: 18 USD
Waste percentage: 15 %
- Convert the 15% discarded share to 0.15.
- Assign $18 × 0.15 = $2.70 to waste.
Example result: $2.70
Frequently asked questions
What if waste contains several foods at different prices?
Use the recorded food-waste scenario to price each discarded quantity with its own matching unit cost. One blended percentage can hide those differences.
Does the answer include lost menu revenue?
No. It allocates the purchase cost. Selling price and lost-sales assumptions are not part of this form.