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U.S. Copper Stockpile Reaches 1.6M Tons as Tariff Arbitrage Fades
The United States is now estimated to hold roughly 1.6 million tonnes of copper as tariff uncertainty continues to distort global metal flows. But the price incentive that pulled copper into U.S. warehouses has narrowed sharply, raising a new question for the market: will the metal keep coming — or eventually start leaving?
By Paul Ploumis
Published October 15, 2026
Key Points
- Estimated U.S. copper stocks: About 1.6 million tonnes on and off exchange, according to Macquarie.
- COMEX stocks: More than 714,000 tonnes, up nearly 750% from the end of February 2025.
- Share of visible stocks: U.S. COMEX warehouses now hold roughly 70% of globally visible exchange copper inventories.
- U.S. LME warehouses: Nearly 130,000 tonnes of registered copper, up 44% since mid-August.
- COMEX-LME arbitrage: About $310/tonne, down from more than $3,000/tonne at its 2025 peak.
- Refined copper tariff: A proposed 15% tariff from January 2027 remains undecided.
- Next major industry event: LME Week runs October 19–23 in London.
SEATTLE (Scrap Monster): The United States has accumulated one of the world's largest commercial copper stockpiles without the federal government directly purchasing the metal, but the market mechanism that brought those tonnes into the country is beginning to weaken.
Macquarie estimates that copper inventories held in the United States, including exchange and off-exchange material, now total approximately 1.6 million tonnes.
At the same time, more than 714,000 tonnes are sitting in COMEX-approved warehouses following an extraordinary buildup that began after the U.S. launched its national-security investigation into copper imports in February 2025.
COMEX stocks have increased by nearly 750% since then.
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The 1.6-million-tonne estimate becomes more striking when compared with normal U.S. copper flows.
The U.S. Geological Survey estimates that American mines produced approximately 1.0 million tonnes of recoverable copper in all of 2025.
That means Macquarie's estimated U.S. stockpile is roughly 1.6 times the country's entire annual mine output.
Reuters also reports that the United States imported more than 1.62 million tonnes of copper in 2025, an 80% increase from 2024.
In other words, today's estimated stockpile is roughly comparable in scale to an entire year of record U.S. copper imports.
| U.S. Copper Measure | Approximate Volume |
|---|---|
| Estimated current U.S. stockpile | 1.60M tonnes |
| 2025 U.S. copper mine production | 1.00M tonnes |
| 2025 U.S. copper imports | 1.62M tonnes |
| Current COMEX warehouse stocks | 714,000+ tonnes |
| U.S. LME registered stocks | ~130,000 tonnes |
Another detail matters.
The roughly 714,000 tonnes on COMEX plus almost 130,000 tonnes registered in U.S. LME warehouses account for only about 844,000 tonnes of the broader 1.6-million-tonne Macquarie estimate.
That suggests a substantial amount of American copper is held outside those two visible exchange warehouse systems.
The figures are based on different reporting systems and timing, so they should not be treated as a precise inventory reconciliation. But they help show why visible exchange stocks alone do not capture the full scale of copper accumulated in the United States.
Data note: ScrapMonster previously reported a U.S. stockpile estimate of approximately 1.1 million tonnes based on Citi analysis. The newer 1.6-million-tonne figure comes from Macquarie and uses a broader estimate of on- and off-exchange stocks. The difference should not be interpreted as a 500,000-tonne inventory increase in a matter of days.
COMEX Now Holds About 70% of Visible Copper Stocks
The geographic imbalance in copper inventories has become extreme.
COMEX-approved warehouses in the United States now hold roughly 70% of the copper visible across the world's major exchanges.
Combined inventories on COMEX, the London Metal Exchange and Shanghai Futures Exchange total just over one million tonnes.
With more than 714,000 tonnes located on COMEX alone, most immediately visible exchange metal is now concentrated in the United States.
This helps explain one of the most unusual features of the current market: analysts can forecast a global copper surplus while physical availability outside the United States remains tight.
Tariff Trade Pulled Copper Into the United States
The buildup began after President Donald Trump ordered a Section 232 investigation into U.S. copper imports in February 2025.
Traders anticipated the possibility that imported refined copper could eventually face tariffs.
That pushed COMEX copper prices above comparable London Metal Exchange prices and created an arbitrage opportunity.
When the U.S. premium was large enough to cover freight, insurance and other costs, traders could purchase copper elsewhere, ship it to the United States and deliver it into COMEX warehouses at a profit.
The result was a major redirection of global copper flows toward the U.S.
COMEX-LME Arbitrage Has Collapsed
The economics of that trade are now much less attractive.
The COMEX premium over LME copper reached more than $3,000 per tonne at its peak in July 2025.
The spread is now closer to $310 per tonne.
| COMEX-LME Arbitrage | Approximate Level |
|---|---|
| Peak in July 2025 | >$3,000/tonne |
| Current level | ~$310/tonne |
That represents a reduction of almost 90% from the peak.
The spread can still support certain trades depending on freight, financing and warehouse costs, but the incentive to continuously pull additional copper into the United States has weakened substantially.
The Stockpile Is Commercial — Not a Government Reserve
The sheer volume of copper stored in the United States has prompted comparisons with a strategic reserve.
There is an important distinction.
Most of today's copper is owned by commercial market participants rather than the U.S. government.
The copper entered the country because traders responded to the COMEX price premium and tariff expectations.
That also means the metal can theoretically leave again.
If copper becomes sufficiently scarce in Europe or Asia, LME or Shanghai prices could rise enough relative to COMEX to reverse the trade.
At that point, exporters could have an economic incentive to move U.S. stocks back into international markets.
The Refined Copper Tariff Remains Unresolved
The White House imposed tariffs on semi-finished copper and copper-intensive derivative products in 2025 and subsequently revised the broader metals tariff regime in 2026.
Refined copper remains the key unresolved category.
The Commerce Department previously recommended a universal tariff of:
- 15% on refined copper beginning January 1, 2027
- 30% beginning January 1, 2028
The July 2025 presidential proclamation directed Commerce to provide an updated assessment of U.S. copper markets by June 30, 2026 so the President could determine whether those additional duties were warranted.
No decision implementing the proposed refined-copper tariff has been publicly announced.
January 1 is therefore a proposed tariff start date, not an automatic tariff deadline.
What Happens if January Arrives Without a Decision?
Macquarie analyst Alice Fox sees one plausible scenario in which January arrives without a final tariff decision.
Under that outcome, the arbitrage could weaken further initially before returning to a level high enough to discourage copper from leaving the United States, but not high enough to attract the extraordinary inflows seen previously.
That could leave the market in an unusual middle ground:
the United States remains oversupplied, but the metal does not immediately flow back to markets where physical copper is tighter.
The result could be continued regional fragmentation even in a globally balanced or surplus market.
U.S. LME Stocks Are Still Rising
Although the broader arbitrage is weakening, copper has continued arriving at some U.S. warehouse locations.
LME warehouses in New Orleans and Baltimore held nearly 130,000 tonnes of registered copper, up approximately 44% since mid-August.
The increase adds to the far larger accumulation on COMEX.
Together, the numbers show how tariff expectations have changed the location of copper inventories without necessarily changing the amount of copper available globally.
Why a Global Surplus Can Still Produce High Prices
This geographic distortion helps resolve an apparent contradiction in the copper market.
Macquarie currently forecasts a global refined-copper surplus of approximately 223,000 tonnes in 2026, with larger surpluses possible from 2027 as mine supply increases.
Yet copper prices have recently traded close to record levels.
A market can have enough copper globally while still experiencing regional shortages if too much of that metal is held in locations where other consumers cannot readily access it.
That is essentially what the tariff-driven U.S. stock buildup has created.
What This Means for Copper Scrap
The refined-copper tariff story is separate from U.S. copper scrap policy, but the two increasingly intersect.
Copper scrap itself was excluded from the original Section 232 copper import tariffs.
However, the 2025 copper proclamation separately directed the Commerce Department to implement a domestic-sales requirement involving 25% of high-quality copper scrap produced in the United States.
The policy is intended to improve access to secondary feedstock for U.S. fabricators and refiners.
For scrap processors and brokers, this means U.S. copper policy is influencing both sides of the market: large volumes of refined copper have accumulated domestically because of tariff expectations, while policymakers are also seeking to retain more high-quality secondary copper feedstock.
The exact commercial impact on individual scrap grades will depend on implementation rules, domestic refining demand, export economics and regional buying competition.
ScrapMonster Intelligence: Copper's Problem Is Location, Not Just Supply
The U.S. inventory buildup changes how the usual “surplus versus deficit” debate should be read.
A global surplus normally suggests excess metal and downward price pressure.
But if much of that surplus is concentrated inside the United States while consumers elsewhere compete for a smaller pool of immediately available copper, prices outside the U.S. can remain firm.
That makes three numbers particularly important:
- 1.6 million tonnes: Macquarie's estimated total U.S. copper inventory.
- 70%: Approximate share of global visible exchange stocks held on COMEX.
- $310/tonne: Current COMEX-LME arbitrage, down sharply from its peak.
The first two numbers describe where copper has gone. The third helps determine whether more copper will follow it.
If the arbitrage keeps shrinking, additional U.S.-bound shipments become less attractive.
If it eventually reverses, the next phase of the trade could be copper moving out of the United States rather than into it.
LME Week Could Put Tariffs at Center Stage
The timing makes the issue particularly relevant ahead of the global metals industry's annual gathering in London.
LME Week 2026 runs October 19–23, with the London Metal Exchange's flagship Metals Seminar taking place Monday, October 19.
U.S. refined-copper tariffs, warehouse inventories, global surpluses and the possibility of reversing trade flows are expected to be major discussion points as producers, traders, consumers and investors assess the 2027 outlook.
What to Watch Next
Refined copper tariff decision: The biggest policy question remains whether the U.S. will implement the proposed 15% tariff beginning in 2027.
COMEX-LME arbitrage: At about $310/tonne, the spread is far below its peak. Further narrowing would reduce the incentive for new U.S.-bound shipments.
COMEX inventories: Stocks above 714,000 tonnes already represent the majority of globally visible exchange copper.
LME and Shanghai premiums: Stronger international physical premiums could eventually create enough pull to draw copper back out of U.S. warehouses.
Scrap policy: Copper recyclers should watch implementation of U.S. domestic-sales requirements affecting high-quality copper scrap.
LME Week: The October 19–23 gathering should provide fresh industry views on how long the U.S. inventory distortion can persist.
ScrapMonster Market Read: The copper tariff trade may be moving into a second phase. For more than a year, the question was how much copper the possibility of U.S. tariffs could pull into American warehouses. With U.S. stocks now estimated around 1.6 million tonnes and the COMEX-LME arbitrage down almost 90% from its peak, the more important question is becoming what keeps those tonnes there. As long as U.S. prices retain enough premium, the inventory may remain effectively trapped. But if physical shortages outside the United States eventually push London or Shanghai prices decisively above COMEX, the same arbitrage mechanism that built America's copper mountain could begin working in reverse.
Sources: Reuters; Macquarie; U.S. Geological Survey; White House; London Metal Exchange.
