Ore Grade and Contained Metal Calculator
Calculate contained metal tonnage from ore grade and ore tonnage.
Convert between g/t, ppm, and percent for gold, silver, copper, and other metals in mining.
Ore Grade Ore grade is the concentration of a valuable metal or mineral in ore. For precious metals (gold, silver): expressed in grams per tonne (g/t) or oz/ton. For base metals (copper, zinc, lead): expressed in percent (%) by weight. For rare earth/specialty metals: expressed in ppm (parts per million). 1 ppm = 1 g/t = 0.0001% by weight.
Contained Metal Calculation Contained metal = Ore tonnage × Grade For gold: Gold (grams) = Ore (tonnes) × Grade (g/t) Gold (troy oz) = Gold (grams) / 31.1035
Recovery and Payable Metal Metallurgical recovery: not all contained metal is recovered during processing. Gold heap leach: 60–80% recovery | CIL/CIP milling: 88–95% recovery Copper flotation: 85–92% | Zinc flotation: 85–93% Payable metal = Contained × Recovery rate
Cut-Off Grade The cut-off grade (COG) is the minimum grade that justifies mining. Below COG = waste; above COG = ore. COG depends on: metal price, mining costs, processing costs, royalties. Gold example: at $1800/oz gold, 5g/t cut-off is common for underground; 0.4–0.8 g/t for open pit.
Unit Conversions 1 troy oz = 31.1035 g | 1 short ton = 907.18 kg | 1 long ton = 1016 kg 1 metric tonne = 1000 kg = 2204.6 lb g/t × 0.02917 = troy oz / short ton 1% = 10 kg/t = 10,000 ppm = 10,000 g/t (for base metals: g/t not used — use %)
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