Strip ratio measures the amount of waste material moved relative to ore mined in an open-pit operation.
A common formula is:
1Strip Ratio = Waste Tonnes Mined ÷ Ore Tonnes MinedA strip ratio of 2.0 means roughly two tonnes of waste are moved for every tonne of ore mined.
Why strip ratio matters
Waste movement consumes equipment time, fuel, labor, maintenance, haul capacity, and other mining resources even though the waste does not directly generate metal revenue.
Higher waste movement can therefore increase mining cost per tonne of ore delivered and can flow through to Total Cash Cost and All-In Sustaining Cost.
Strip ratio is not ore grade
Ore Grade measures metal concentration in ore. Strip ratio measures waste movement relative to ore.
The two interact economically but answer different questions.
A high-grade zone with a high strip ratio can still be costly to access. A lower-grade deposit with a very low strip ratio may be economically competitive because less waste must be moved.
Period strip ratio versus life-of-mine strip ratio
Mine plans often disclose a life-of-mine average strip ratio.
Actual annual or quarterly strip ratio can differ substantially because mining is sequenced through different phases of the pit.
Early years can require substantial pre-stripping to expose future ore. Later years may have lower or higher ratios depending on pit geometry.
Investors should not assume a single period's ratio represents the full mine life.
Pre-stripping and capitalized stripping
Some waste-removal costs create access to ore that will be mined in future periods.
Under applicable accounting rules, qualifying stripping costs may be capitalized rather than expensed immediately.
That means a high current strip ratio can affect both operating expense and capital expenditure depending on the activity and accounting treatment.
This connects strip ratio to Sustaining Capital Expenditures, but the two remain distinct: one is a physical mining ratio and the other is a financial capital classification.
Higher strip ratio is not automatically worse
A higher ratio generally means more waste movement, but mine economics also depend on:
- ore grade;
- recovery;
- haul distance;
- rock characteristics;
- equipment productivity;
- pit depth;
- mine design;
- fuel and labor cost;
- metal prices; and
- capitalized stripping treatment.
A mine can accept a higher strip ratio to reach materially higher-grade ore or a larger reserve base.
Strip ratio and cutoff decisions
Changes in commodity price, costs, or mine design can alter which material is treated as economic ore versus waste.
That can change the modeled strip ratio even if the geology itself has not changed.
The metric should therefore be interpreted within the same mine-plan assumptions used for reserve estimation and production scheduling.
Underground mines are different
Strip ratio is primarily an open-pit concept.
Underground mines have different development, access, dilution, and waste-handling economics. Applying an open-pit strip ratio framework directly to underground operations can be misleading.
Filing examples
Dakota Gold's 2025 Form 10-K reports life-of-mine strip ratio alongside tonnes processed, feed grade, recovery, sustaining capital, total cash cost, and AISC. That illustrates why strip ratio is best read as one physical driver within a broader mine-economics system.
Sources:
Bottom line
Strip ratio measures waste-to-ore movement, not profitability by itself. It becomes useful when paired with grade, recovery, haul distance, mine sequencing, and the accounting treatment of stripping costs.
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