LME vs COMEX copper: why the prices differ and what the spread means for buyers
Copper has two main benchmarks: the LME in London and COMEX in New York. They are quoted in different units and traded in different places, so they rarely show the same number. Here is how to compare them and why the gap moves.
Two benchmarks for one metal
The London Metal Exchange (LME) is the global benchmark for physical copper. Its price is quoted in US dollars per tonne for Grade A cathode, delivered from LME-approved warehouses around the world. COMEX, part of CME Group in New York, lists copper futures quoted in US dollars per pound, with delivery from warehouses in the United States and contracts by delivery month. They track the same metal, but they are separate markets with different stocks, delivery points and participants.
How to compare them in the same unit
COMEX price per tonne = COMEX price per pound × 2,204.62
The figures below are illustrative, not market prices.
| Quoted as | Per tonne | |
|---|---|---|
| COMEX copper | $4.50 per pound | $9,921 |
| LME copper | $9,600 per tonne | $9,600 |
| Spread (COMEX minus LME) | $321 |
What moves the spread
- Trade policy and tariffs. Expectations of US import tariffs pull metal toward the US and lift COMEX against the LME. In 2025 tariff announcements widened the gap sharply, and it narrowed again as the policy changed.
- Stocks in each market. Low inventories in US warehouses support COMEX; ample LME stocks weigh on the LME price.
- Freight and delivery time. The cost and time of moving metal to the US set how far COMEX can sit above the LME before shipping it pays.
- Contract structure. COMEX trades by delivery month; the LME trades daily prompt dates. The dates matter when you compare.
Which benchmark should a contract follow?
It depends on where the metal is delivered and what the supplier uses. US buyers are often priced off COMEX plus a premium, while buyers in Europe and Asia are usually priced off the LME. Whichever it is, the contract should name the benchmark, the averaging period and the premium. See copper cathode premium explained for the premium part.
What the spread means for purchase price variance
If the standard cost was built from the LME price and the invoice is priced off COMEX, the spread appears as variance even if the LME price never moved. Report the spread as its own line in the variance split; the purchase price variance guide shows how. MetalAlert's probabilities are about the LME copper price; see the copper price forecast for what they cover.
Common questions
Why is COMEX copper usually higher than LME copper?
Because COMEX is priced for delivery in the United States. Freight, import duties or expected tariffs, and US stock levels all add to the price there, and the gap varies as those factors change.
How do you convert COMEX copper to a price per tonne?
Multiply the COMEX price per pound by 2,204.62. For example, $4.50 per pound is about $9,921 per tonne, which you can compare with the LME price per tonne.
Which is the global benchmark for copper, LME or COMEX?
The LME is the global benchmark for physical copper. COMEX is the main benchmark in the United States, and many US contracts are priced off it.
What is the COMEX-LME copper spread?
It is the difference between the COMEX price, converted to dollars per tonne, and the LME price. It widens when conditions pull metal toward the United States and narrows when they ease.
Does MetalAlert forecast COMEX or LME copper?
MetalAlert's probabilities are about the LME copper price. They do not cover the COMEX price or the spread between the two.
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