Ore Grade Concentration Calculator
This calculator determines the contained metal content in an ore body from tonnage and grade. Ore grade is the mass fraction of a target metal in the total ore mass. The formula is contained metal = tonnage x grade, applied consistently across the units you select. This calculation is the basis of all mineral resource estimates and is used in feasibility studies and environmental impact assessments for mining projects.
Ore grade formula
Contained Metal = Tonnage (t) x Grade (g/t) / 1,000,000 x 1,000,000 g/t
For grade in percent: Contained Metal (tonnes) = Tonnage x (Grade / 100). For grade in g/t: Contained Metal (grams) = Tonnage x Grade. For grade in ppm: same as g/t (1 ppm = 1 g/t by mass).
Typical ore grades by commodity
| Metal | Typical Grade Unit | Marginal Grade | High Grade |
|---|---|---|---|
| Gold | g/t | 0.5 g/t | 5+ g/t |
| Copper | % | 0.2% | 2%+ |
| Silver | g/t | 30 g/t | 300+ g/t |
| Zinc | % | 3% | 10%+ |
| Iron | % | 25% | 65%+ |
Ore grade concentration calculator: frequently asked questions
What is ore grade?
Ore grade is the concentration of a valuable mineral or metal within an ore body, typically expressed as a percentage (for base metals like copper), grams per tonne (for precious metals like gold and silver), or parts per million (ppm). Higher grade ore contains more valuable metal per unit of rock.
How is contained metal calculated?
Contained metal = ore tonnage x grade. For example, 100,000 tonnes of ore at 1.5% copper contains 1,500 tonnes of copper. For gold at 2 g/t, 100,000 tonnes contains 200,000 grams (200 kg) of gold.
What is the difference between g/t and ppm?
Grams per tonne (g/t) and parts per million (ppm) are numerically equivalent for mass concentrations: 1 g/t = 1 ppm. Both describe 1 part of metal per 1,000,000 parts of rock by mass.
What is a cut-off grade?
The cut-off grade is the minimum ore grade at which it is economically viable to mine and process ore. Rock below the cut-off grade is treated as waste. Cut-off grades depend on commodity prices, mining costs, and metallurgical recovery rates.
How does this relate to JORC or NI 43-101 reporting?
Mineral resource and reserve reporting under JORC Code (Australia) and NI 43-101 (Canada) requires disclosure of ore grade alongside tonnage and cut-off grade. This calculator performs the standard grade-times-tonnage calculation used in resource estimates, but formal reserve estimates require a Competent Person or Qualified Person sign-off.
Official sources
- U.S. Geological Survey (USGS) Mineral Resources Program: USGS Mineral Resources Program.
- JORC Code 2012 (Joint Ore Reserves Committee): JORC Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.