What is cut-off grade?

Cut-off grade (COG) is the minimum metal grade at which ore can be profitably mined and processed. Material above the COG is classified as ore; material below it is classified as waste (or low-grade stockpile). It is the single most important parameter in mine planning.

What is the break-even COG formula?

Break-even COG = (Operating Cost per tonne) / (Metal Price × Recovery × Payability × Unit Conversion Factor). Royalties and refining charges are subtracted from the effective metal price before dividing.

What units does this calculator use for gold versus copper?

For gold (price in USD/troy oz), the result is in grams per tonne (g/t). For copper or other base metals priced per pound, select "% metal" and the tool converts internally using the appropriate factor. You can also enter a custom unit conversion.

Does this include capital cost recovery?

No. This calculator computes the operating (cash) cut-off grade, which excludes capital cost amortization. To include capital, add an equivalent per-tonne capital charge to the operating cost input.

Payability is the percentage of the recovered metal content that the smelter or refinery actually pays for. For example, a copper smelter might pay for 96.5% of the copper in concentrate after subtracting treatment charges. Gold in dore is typically paid at 99.9%.

What is metallurgical recovery?

Metallurgical recovery is the fraction of the metal present in the ore that is successfully extracted during processing. A gold heap-leach operation might recover 70%; a flotation circuit for copper might recover 88%. Higher recovery lowers the cut-off grade.

Cut Off Grade Calculator

Name: Cut Off Grade Calculator
Availability: InStock
Author: Nham Vu

Enter your mining costs, metal price, metallurgical recovery, and payability to calculate the minimum ore grade required to break even.

Operating Parameters

Metal / Commodity

Metal Price (USD / troy oz)

Total Operating Cost (USD / tonne ore)

Include mining + milling + G&A costs per ore tonne.

Metallurgical Recovery (%)

Smelter Payability (%)

Optional Deductions

Royalty Rate (%)

Refining Charge (USD/t ore)

Enter parameters on the left and click Calculate COG

Break-Even Cut-Off Grade

— g/t

Any ore block grading above this value covers its operating costs.

Price Sensitivity — COG vs. Metal Price

Metal Price	COG	vs. Base

Calculation Breakdown

Formula: COG = (Opex + Refining Charge) / (Metal Price × (1 − Royalty%) × Recovery% × Payability% × Conversion Factor)

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Summary

Enter your mining costs, metal price, metallurgical recovery, and payability to calculate the minimum ore grade required to break even.

How it works

Enter the total operating cost per tonne of ore processed (mining + milling + G&A).
Enter the current metal price in your chosen currency per unit (e.g., USD per troy oz for gold).
Enter the metallurgical recovery as a percentage (the fraction of metal in ore that is recovered to concentrate or dore).
Enter the smelter payability as a percentage (the fraction of recovered metal that the refiner pays for, after deductions).
Optionally enter a royalty rate and refining charge to see their effect on COG.
Click Calculate to get the break-even cut-off grade in grams per tonne (g/t) or percent (%) depending on the metal unit selected.

Use cases

Determining whether a low-grade ore block should be sent to the mill or to waste.
Sensitivity analysis: how does COG change when metal price drops 20%?
Comparing open-pit versus underground economics on the same deposit.
Scoping studies and prefeasibility mine planning.
Teaching mineral economics to geology and mining engineering students.
Quickly checking a contractor's or consultant's COG assumptions.
Evaluating marginal ore stockpile decisions at existing operations.

Frequently Asked Questions

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Last updated: 2026-05-23 · Reviewed by Nham Vu