Overburden Stripping Ratio Calculator
This calculator determines the overburden stripping ratio for an open-pit mine from waste and ore quantities, and also computes the break-even stripping ratio from economic parameters. The stripping ratio is the fundamental metric determining whether open-pit or underground mining is appropriate, and it drives open-pit mine cost models globally.
Stripping ratio formula
SR = Waste (t) / Ore (t) BESR = Revenue/t(ore) / Mining cost/t(waste)
Where SR is the stripping ratio (dimensionless), BESR is the break-even stripping ratio. If SR is less than BESR, the mine is economic. If SR exceeds BESR, underground mining or selective mining methods should be considered.
Typical stripping ratios by commodity
| Commodity | Typical SR Range | Maximum Economic SR |
|---|---|---|
| Coal (bulk) | 1:1 - 8:1 | 10-15:1 |
| Iron ore | 0.5:1 - 4:1 | 6:1 |
| Copper porphyry | 2:1 - 10:1 | 20:1 |
| Gold (bulk) | 3:1 - 15:1 | 35:1 (high grade) |
| Bauxite | 0.1:1 - 1:1 | 3:1 |
Overburden stripping ratio calculator: frequently asked questions
What is the stripping ratio in mining?
The stripping ratio (SR) is the amount of waste rock (overburden) that must be removed to expose and extract a unit of ore. It is expressed as tonnes of waste per tonne of ore (t:t) or cubic metres of waste per tonne of ore (BCM/t). A lower stripping ratio means the deposit is cheaper to mine.
How is stripping ratio calculated?
Stripping Ratio = Waste Tonnage / Ore Tonnage. If 3,000,000 tonnes of waste must be removed to mine 1,000,000 tonnes of ore, the stripping ratio is 3:1 (or simply 3). It may also be expressed by volume: waste BCM (bank cubic metres) / ore tonne.
What is the break-even stripping ratio?
The break-even stripping ratio (BESR) is the maximum stripping ratio at which it remains economic to mine. BESR = (Revenue per tonne ore - Processing cost per tonne ore) / Mining cost per BCM waste. At the BESR, the incremental revenue from ore just covers the cost of removing the waste above it.
How does stripping ratio affect project economics?
Stripping ratio is a primary driver of open-pit mining costs. Higher ratios mean more waste must be moved per tonne of ore, increasing haulage and fuel costs. A project with a stripping ratio above the BESR would be better mined using underground methods or left in the ground.
What is a typical stripping ratio for open-pit mines?
Economic open-pit mines typically operate at stripping ratios of 1:1 to 8:1 (waste:ore) for low-value bulk commodities like coal and iron ore. For high-value metals like gold and copper, ratios of 3:1 to 20:1 can be economic. Very high grade gold deposits may justify ratios above 30:1.
Official sources
- U.S. Office of Surface Mining Reclamation and Enforcement: OSMRE Technical Reference.
- U.S. Geological Survey (USGS) Mineral Resources: USGS Mineral Resource Assessments.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.