Why adjustment clauses exist
Copper and aluminium make up roughly 80% of the cost of a typical wire or cable product, according to listed Chinese cable makers' disclosures, and the industry's general pricing model is copper price plus processing fee. That works well for a single order quoted and confirmed within a few days. It works badly for a project with call-offs over six or twelve months, a framework agreement with a distributor, or a tender where the award comes weeks after the bid.
In those cases a fixed price forces the plant to add a risk margin, and if copper moves sharply the side that loses has an incentive to renegotiate or cut corners. Copper does move: LME three-month copper reached a record intraday high of USD 14,875 per tonne on 10 September 2026 (Fastmarkets) and was about USD 14,315 per tonne on 21 October 2026 (Investing News). A clause that ties the copper part of the price to a public benchmark lets both sides price the processing work fairly and leave metal risk to a formula. The background on how quotes are built is in copper price and cable quotes.
Formula shape 1: the index formula
The first common shape, used in published escalation clause examples by large electrical equipment buyers, splits the price into a fixed share and one or more indexed shares:
P1 = P0 x ( a + b x Cu1 / Cu0 + c x M1 / M0 )
- P0 is the contract price on the base date and P1 the adjusted price.
- a is the fixed share (processing, overhead, margin) that does not move with metal.
- b is the copper share; Cu0 and Cu1 are the copper benchmark on the base date and on the adjustment date.
- c x M1 / M0 is an optional share for another input, such as aluminium, steel or a compound index.
- The shares add up to one.
The strength of this shape is that it handles a whole price, including several inputs, with one line. Its weakness is that the shares are an agreed estimate. If the copper share is set too high or too low for a given construction, the adjustment over- or under-compensates. It suits framework prices across many sizes where calculating copper weight for every line would be heavy.
Formula shape 2: weight times price difference
The second shape, seen in public tender answers from international development procurement, adjusts by the actual metal content:
A = Wcu x (Cu - Cu0) / 1000 + Wal x (Al - Al0) / 1000
- A is the adjustment per kilometre of cable, added to or deducted from the base price.
- Wcu and Wal are the copper and aluminium weights in kg per km for that construction, from the spec sheet.
- Cu and Al are the benchmark prices per tonne on the fixing date; Cu0 and Al0 are the base prices in the bid. Dividing by 1000 converts tonnes to kilograms.
- In the published example the fixing date was the day after the letter of credit or advance payment arrived, using the LME cash settlement price.
This shape is more precise, because it uses the real metal weight of each size. It needs a stated conductor weight per km for every line, which the plant can derive from the cross-section and conductor class. It suits project schedules with a limited number of sizes.
| Point | Index formula | Weight x price difference |
|---|---|---|
| Inputs needed | Agreed shares, base and current index | Metal weight per km, base and current price |
| Precision | Depends on how well shares are set | Follows actual metal content |
| Best for | Framework prices across many sizes | Project schedules with defined sizes |
| Other inputs | Easy to add steel or compound index | Usually metal only |
| Main dispute risk | Share values | Weight per km and fixing date |
Variants you will meet
European suppliers often express the same idea as a copper base plus a copper surcharge. The list price includes copper at a stated base value, and a surcharge equal to the difference between the current copper quotation and that base is added per kilogram of copper content. Some suppliers use the previous month's average LME price to set the next month's surcharge. In wider conductor industry practice, buyers can also choose between a spot fix on a stated date, a monthly average, or an average over a window the customer selects, and that choice is written into the contract.
Whichever variant you use, the mechanics are the same: a public benchmark, a base value, a fixing date and a way to apply the difference to each line. For aluminium conductor lines, such as those on our aluminium cables page, state the aluminium benchmark separately rather than assuming it tracks copper.
What to write into the clause
- Benchmark: exact source and series, for example LME cash settlement or three-month, or a named domestic price.
- Base value and base date: the copper (and aluminium) figure built into the contract price.
- Fixing trigger: order confirmation, deposit received, L/C opened, or a monthly average before shipment.
- Weights or shares: copper weight per km for each size, or the agreed shares in the index formula.
- Band: optional threshold below which no adjustment applies, so small moves do not generate paperwork.
- Direction: the clause adjusts both up and down.
- Evidence: how the benchmark is documented for each invoice.
Payment terms interact with the fixing trigger. If copper is fixed when the deposit arrives, a late deposit moves the price; the Incoterms and payment guide covers the common combinations. None of this is legal advice; have your own contract adviser review the final wording.
How the desk uses these clauses
For single orders we usually recommend a fixed price within the quote validity, locked on deposit. For framework agreements and project schedules, the desk proposes one of the two shapes above, asks each partner factory to state metal weights per km on the spec sheet, and checks the benchmark on each invoice. That keeps quotes comparable and makes the adjustment auditable. More on pricing structure is in the cable pricing guide; for project volumes and timing see MOQ and lead time, or send your schedule through the quote form.