Breakeven Cutoff Grade
The cutoff grade is where a tonne of rock stops paying for its own processing, the boundary between ore and waste.
The equation
cutoff = cost per tonne / (price × recovery)
- Costs include mining, processing, and overheads per tonne treated
- Price is per unit of metal, recovery the fraction the plant captures
- Grades below cutoff lose money even though they contain metal
Worked example
With 42 dollars per tonne of costs, gold at 60 dollars per gram, and 92 percent plant recovery, the breakeven cutoff is 42 / (60 × 0.92) = 0.76 grams per tonne. A blocked out zone at 0.6 grams per tonne is mineralization, not ore.
When to use it
Marginal cutoffs for material already mined exclude mining cost, which is why stockpile decisions use a lower bar. Cutoff policy over a mine life is an optimization, not a single division.
Related Calculators and Reference
- Cutoff Grade Calculator: breakeven grades from your own costs.
- Grade Tonnage Curve Calculator: see the whole deposit response to cutoff.
- CIM: source of reporting standards for mineral resources.