Cut-Off Grade Explained: How Miners Decide What Is Economic

Summary box

• Cut-off grade explained: it is the minimum grade required for ore to be economic.


• Cut-off grade changes with metal price, recovery, costs, and mining method.


• Raising cut-off grade can shrink reserves and shorten mine life.


• Investors should validate cut-off assumptions in technical reports.

Last updated: 2026-02-01

Cut-off grade explained in plain terms: it is the grade threshold that separates ore from waste. It determines how much of a deposit is economic and has a direct impact on reserves, mine life, and valuation. A small change in cut-off grade can dramatically change project economics.

Use Mining Terminal's filings to review technical reports and projects to compare cut-off grades across similar deposits. For valuation context, see mining stock valuation methods.

What is cut-off grade?

Cut-off grade is the minimum grade at which a tonne of material generates positive economic value. Material above the cut-off is considered ore; material below it is waste. The cut-off grade is not a fixed number, and it changes as prices, costs, and recoveries change.

In practice, cut-off grade is one of the most important inputs in mine planning. It determines the size of reserves and the expected production profile. Investors should treat it as a core risk factor, not a footnote.

Cut-off grade explained: the basic formula

A simplified cut-off grade formula looks like this:

• Cut-off grade = (Mining cost + Processing cost + G&A) / (Metal price x Recovery x Payability)

This formula shows why cut-off grade changes:

• Higher prices reduce the cut-off grade.
• Higher costs increase the cut-off grade.
• Better recovery reduces the cut-off grade.
• Worse payability increases the cut-off grade.

Real-world models are more complex, but the logic is the same. Use metallurgical recovery explained for recovery context.

Why cut-off grade matters for investors

Cut-off grade determines:

• Reserve size: Higher cut-off means fewer tonnes qualify as reserves.
• Mine life: Higher cut-off reduces the economic life of a mine.
• Grade profile: Higher cut-off increases average grade but reduces tonnage.
• Cash flow timing: Higher cut-off may bring higher grades forward, increasing early cash flow.

Investors should compare cut-off grades across peer projects to gauge whether a company is conservative or aggressive.

Cut-off grade vs break-even grade

Cut-off grade is sometimes confused with break-even grade. The break-even grade is the grade at which cash flow is zero. The cut-off grade is often set higher than break-even to ensure a margin and account for uncertainty.

Projects with cut-off grades close to break-even are fragile because any cost increase or price decline can make the ore uneconomic.

Related reading: mining jurisdiction checklist.

Cut-off grade explained: a simple worked example

Investors do not need a full mine model to sanity check cut-off grade. A simplified example can show the logic.

Assume a copper project with total cost of $45 per tonne of ore. One percent copper equals about 22 pounds of copper per tonne. If copper is $4 per pound, recovery is 85 percent, and payability is 95 percent, then the payable value per tonne is 22 x 4 x 0.85 x 0.95, or roughly $71 per tonne. At 1 percent copper, this tonne is economic. The cut-off grade is the grade where the payable value equals $45 per tonne.

If prices drop, recovery falls, or costs rise, the cut-off grade increases. This is why a small change in assumptions can change which material is treated as ore.
Use mining project risk checklist to stress-test the cost and recovery inputs behind the example.

Cut-off grade vs NSR and equivalent grade

Polymetallic deposits often use net smelter return (NSR) or equivalent grades instead of a single metal grade. NSR translates multiple metals into a per-tonne value after recovery and payability. Equivalent grade converts that value into the grade of a chosen metal.

When screening stocks, the key is the assumptions behind NSR: metal prices, recoveries, payability, and penalties. If those inputs are optimistic, the cut-off grade is understated. If a project uses equivalent grades, verify that the conversion formula is consistent with current terms and realistic recoveries. Use mining stock valuation methods to connect NSR assumptions with valuation inputs.

By-product credits and cut-off grade

By-product credits can materially lower cut-off grade. For example, a copper mine with meaningful gold or silver credits may report a lower copper cut-off because by-product revenue reduces the net cost per tonne. This can expand reserves and extend mine life, but only if the by-product assumptions are realistic.

Investors should check whether by-product price assumptions and recoveries are disclosed. If by-product prices are set aggressively, the cut-off grade may be too low. Compare the by-product assumptions with recent price ranges and peer disclosures in filings.

How cut-off grade changes over the mine life

Cut-off grade is not static. Many mines use multiple cut-off grades:

• Initial cut-off: Set to maximize early cash flow.
• Marginal cut-off: Lower grade used later to extend mine life.
• Stockpile cut-off: Low-grade material stored for potential future processing.

This is why a mine can show both high average grades early and lower grades later. Investors should read the life-of-mine plan to see how cut-off grade evolves over time.

Mining method and cut-off grade

Mining method affects cut-off grade:

• Open pit: Generally lower cut-off grades because costs per tonne are lower.
• Underground: Higher cut-off grades because costs are higher.

If an open pit project reports a high cut-off grade, it may signal high costs or poor recovery. If an underground project reports a low cut-off grade, it may signal aggressive assumptions.

Use underground vs open pit mining for additional context.

Cut-off grade and strip ratio

In open pits, cut-off grade is linked to strip ratio. A higher strip ratio increases mining cost per tonne, which raises the cut-off grade. When a company updates pit designs, the cut-off grade can shift even if costs and prices are unchanged.

Investors should check whether a cut-off grade change is driven by a new pit shell or a change in strip ratio assumptions. If strip ratio has increased, the project may be more sensitive to cost inflation. Use strip ratio explained to connect pit design choices with economics.

Cut-off grade and plant throughput constraints

Processing capacity can create a practical cut-off grade. If a plant is constrained, operators may raise cut-off grade to prioritize higher-value material and maximize cash flow. If capacity expands, the cut-off grade may fall and more material becomes economic.

Investors should check whether the study assumes debottlenecking or plant expansion. A low cut-off grade that depends on future capacity may be optimistic if funding is not secured. Use mining project financing options to assess whether capacity expansion is realistic.

Processing route and cut-off grade

Processing complexity affects cut-off grade. A simple gravity or heap leach operation may support a lower cut-off. A complex processing route with high reagent costs increases cut-off grade.

If a project depends on pre-treatment such as pressure oxidation, investors should check whether the added costs are reflected in cut-off grade assumptions.

Recovery and cut-off grade

Recovery is a key driver of cut-off grade. Lower recovery increases cut-off grade because less metal is recovered per tonne. If recovery assumptions are optimistic, the cut-off grade may be understated.

Use metallurgical recovery explained to understand how recovery uncertainty affects economics.

Payability and smelter terms

Payability affects cut-off grade because it determines how much metal is paid for after smelting and refining. If payability is low, the cut-off grade increases.

For concentrates, check whether penalties for impurities are included. If not, cut-off grade may be too low.

Cut-off grade and reserve reporting

Reserves are reported based on cut-off grade. If a company uses a lower cut-off than peers, it may report larger reserves, but those reserves may be less economic.

Investors should compare reserve grades with cut-off grades and evaluate whether reserves are strong at realistic prices.

Use mining reserves vs resources explained to understand how reserves are reported.

Reporting standards and definitions

Cut-off grade is embedded in reserve definitions and disclosure rules. Canadian reporting uses CIM Definition Standards, which guide how reserves and resources are described in NI 43-101 technical reports. US reporting under SEC S-K 1300 has similar disclosure requirements for economic assumptions and reserve definitions.

Investors should confirm that a report clearly states the price, recovery, and cost assumptions used to set cut-off grade. If those assumptions are missing or outdated, the reserve numbers are less reliable. Use reading NI 43-101 reports to verify that critical assumptions are disclosed.

Sensitivity analysis: how to test cut-off assumptions

Most technical reports include sensitivity tables. Investors should look for:

• Cut-off grade sensitivity to price changes.
• Sensitivity to recovery assumptions.
• Impact on reserves and mine life.

If small changes cause large reserve reductions, the project is higher risk.

Cut-off grade optimization and scheduling

Companies often optimize cut-off grade to maximize project value, not simply to maximize tonnes. Higher cut-off grades can increase early cash flow by prioritizing higher-grade material. Lower cut-off grades can extend mine life and use existing infrastructure longer.

Investors should review the life-of-mine schedule to see how cut-off grade changes over time. A project that front-loads high-grade material may look strong early but can face declining grades later. Use mining feasibility study checklist to evaluate scheduling assumptions.

Related reading: mining stock catalysts, AISC explained guide, mining portfolio construction, and build a mining stocks watchlist. Additional context: mining stocks overview, and mining stocks list.

Cut-off grade and the block model

Cut-off grade is applied to the block model, which is the 3D representation of the orebody used for mine planning. Each block has an estimated grade, density, and recovery. When the cut-off grade changes, the mineable blocks change, which can alter the pit shell, stope shapes, and reserve tonnage.

This is why a cut-off grade adjustment can change more than just reserve totals. It can shift which zones are mined first, change strip ratios, and alter the production profile. Investors should look for clear disclosure of the block model assumptions in technical reports and confirm that the cut-off grade is applied consistently.

Cut-off grade in different commodities

Cut-off grade varies by commodity:

• Gold: Cut-off often expressed in g/t.
• Copper: Often expressed in percent.
• Uranium: Often expressed in ppm or percent.
• Coal: May be based on calorific value or quality specs.

Comparing cut-off grades across commodities is meaningless. Compare within the same commodity and mining method.

Cut-off grade and commodity cycles

Cut-off grades are often adjusted across cycles. In strong markets, companies may lower cut-off grades to expand reserves. In weak markets, they may raise cut-off grades to protect margins.

This means reserve size can change even without new drilling. Investors should track the price assumptions used in reserve updates.

Use commodity cycles guide for cycle context.

Cost inflation, energy prices, and currency effects

Cut-off grade is sensitive to operating costs. Diesel, power, labor, and reagent inflation all raise the break-even value per tonne, which pushes cut-off grade higher. In global mining, currency moves also matter because costs are often in local currency while revenue is in US dollars.

Investors should check whether a report uses outdated cost assumptions. If costs have risen since the study date, the effective cut-off grade today may be higher than reported. Use mining project risk checklist to stress-test cost assumptions.

Price deck transparency and scenario testing

Cut-off grade depends on the price deck used in the study. If a company uses a bullish price deck, the cut-off grade may be lower than what would be economic at consensus prices. This can inflate reserves and make the mine life look longer than it is.

Investors should check whether the price deck is stated and whether sensitivity analysis is provided for lower prices. If a project only works at high prices, the cut-off grade is fragile. Use commodity cycles guide to align price assumptions with cycle risk.

How to evaluate cut-off grade in a technical report

Use this checklist:

• Identify the cut-off grade in the reserve and resource tables.
• Check the price assumptions used to calculate it.
• Review recovery and payability assumptions.
• Compare cut-off grade to peer projects.
• Check whether the cut-off is updated for cost inflation.

If the report is outdated, the cut-off grade may be too low for current costs.

Cut-off grade and mine life

A higher cut-off grade often shortens mine life but increases early cash flow. A lower cut-off extends mine life but may reduce margins.

This is a classic trade-off. Investors should decide whether they prefer near-term cash flow or long-term stability.

Use mine life reserve life index for more on mine life.

Cut-off grade and stockpile strategy

Many mines use stockpiles to manage cut-off grade. Material below the plant cut-off can be stockpiled and processed later if prices improve or costs fall. This can create upside, but it also adds operational complexity and working capital needs.

Investors should confirm whether stockpiled material is included in reserve or only resources. If a company treats stockpile material as reserves without clear economics, the project may be overstated.

Mining dilution and ore loss

Cut-off grade is a planning input, but real mining introduces dilution and ore loss. Dilution occurs when waste is mixed into ore during blasting and loading, which reduces delivered grade. Ore loss occurs when some ore is left behind. Both effects can raise the effective cut-off grade needed to stay economic.

Investors should check whether the study uses realistic dilution and ore loss assumptions. If a project relies on very low dilution despite complex geology, the cut-off grade may be too optimistic. For financial dilution risk, see dilution and recovery mining.

Cut-off grade and stockpiles

Low-grade stockpiles are common. Companies may stockpile material below the current cut-off and process it later if prices rise.

Stockpiles provide optionality but should not be valued the same as reserves. Investors should treat stockpiles as upside, not core value.

Common mistakes when interpreting cut-off grade

• Comparing cut-off grades across different commodities.
• Ignoring recovery and payability assumptions.
• Assuming cut-off grade is static across cycles.
• Treating a low cut-off grade as always positive.

Cut-off grade must be evaluated in context.

Red flags in cut-off grade assumptions

Watch for these common issues:

• Cut-off grade set without updated costs or recovery testwork.
• Cut-off grade materially lower than peers with similar mining methods.
• Reserve tables that omit the price and recovery assumptions.
• Mine plans that rely on aggressive cut-off grades to keep mine life long.

If you see these patterns, re-check the technical report assumptions and compare with peers in projects.

How cut-off grade affects valuation

Valuation models depend on reserves and cash flow. If cut-off grade assumptions are aggressive, valuation can be overstated.

Use mining stock valuation methods to compare valuation inputs across peers.

Tracking cut-off grade changes over time

Cut-off grade is dynamic, so investors should track how it changes across study updates. If a project raises its cut-off grade in a new study, reserves and mine life can decline even if the deposit has grown.

Look for a table of economic assumptions in each update and compare them to prior disclosures. If costs have increased or recovery assumptions have changed, the cut-off grade shift may be justified. If the assumptions are similar but the cut-off grade still rises, the orebody may be more complex than expected.

Use filings to review historical technical reports and compare the evolution of cut-off grade assumptions.

Practical case: cut-off grade shift

Imagine a gold project with a cut-off grade of 0.6 g/t at $1,900 gold. If gold drops to $1,500 or costs rise, the cut-off might increase to 0.9 g/t. This reduces reserves and shortens mine life, even if the orebody has not changed.

This is why investors should focus on the assumptions rather than the headline reserve size.

Investors should model multiple price decks rather than a single base case. A project that looks strong at one price may be fragile when price and cost assumptions are stressed. Even a small price or cost change can move the cut-off grade enough to alter the reserve base.
Test at least two price decks and a higher cost case to see how sensitive reserves are to small assumption changes.

Related reading: mining permitting timeline guide.

Comparing cut-off grades across peers

Cut-off grade comparisons should be done within the same commodity, mining method, and jurisdiction. A low cut-off grade in an open pit gold mine may be normal, while the same cut-off in an underground mine could be aggressive.

When comparing peers, check the study date, price deck, recovery assumptions, and mining method. Use projects to benchmark peer deposits and filings to verify the underlying assumptions.

Using Mining Terminal to compare cut-off grades

Mining Terminal can help investors:

• Compare reserve grades and cut-off grades in projects.
• Review technical report assumptions in filings.
• Benchmark peers and valuation in stocks.

Frequently Asked Questions

What is cut-off grade?
Cut-off grade is the minimum grade required for ore to be economic.

Why does cut-off grade change?
It changes with prices, costs, recovery, and payability assumptions.

Is a lower cut-off grade always better?
Not necessarily. A lower cut-off can include marginal material that lowers margins.

How do I check cut-off grade assumptions?
Review technical reports and compare with peers in similar commodities.

How does cut-off grade affect mine life?
Higher cut-off grades reduce reserves and shorten mine life, while lower cut-off grades extend mine life.

Sources

• Company technical reports and filings
• Mining Terminal data
• CIM Definition Standards (mineral resources and mineral reserves)
• SEC S-K 1300 mining property disclosure rules

Related reading: cut-off grade explained.

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Disclaimer: This analysis is provided for informational purposes only and does not constitute investment advice. Mining Terminal is not a registered investment advisor. Mining stocks carry significant risks including commodity price volatility, operational challenges, and regulatory changes. Always conduct your own research and consult with a qualified financial advisor before making investment decisions. Data sourced from company filings and may not reflect the most recent developments.