Raw-material index pricing for part prices

When commodity prices rise, suppliers write asking for an increase. When they fall, the letters are rarer. Index-linked pricing replaces that asymmetry with a formula both sides agreed in advance.

The principle

A part’s price has a material share and a conversion share. Only the material share follows commodity markets. Index pricing moves that share, and only that share, with a published index.

Illustrative. The material share of the price steps at agreed review periods, up and down, with the index.

What you need

1. Material content per part. The gross weight consumed (net weight plus cutting loss, runners or scrap) and the grade. This is the foundation; if it is wrong, every adjustment is wrong.
2. The index. Published regularly, independent, and representative of the grade and region you buy.
3. A base value. The index value the current price was set against.
4. A review period and lag. For example, quarterly, using the previous quarter’s average.
5. A formula. Material adjustment = gross weight × (new − base material index) − recovered scrap weight × (new − base scrap index). Where the index is quoted in a different unit or form than the grade you buy, agree a fixed factor that converts it.

Each grade needs its own published index and a fixed gross weight per part. Photo: mastars MT, Unsplash.

Making it work in practice

• Calculate material content from the part, not from the invoice. A should-cost gives the gross weight directly from geometry and process.
• Keep the index and the grade matched. An index for one alloy applied to another introduces a permanent error.
• Publish the calculation. Each adjustment should be reproducible by both parties from public numbers.
• Apply it both ways. A clause that only moves up will not survive the first falling market.

Polymer granules follow their own indices; the clause should name the grade. Photo: Alexander Grey, Unsplash.

Beyond the clause

Index data is also a negotiation tool without a clause: tracking commodity movements across your part portfolio shows which suppliers’ price requests are justified, and comparing the material rates you pay with market and competitor rates exposes gaps.

A checklist for introducing index pricing

1. Calculate gross material content per part from geometry and process, not from invoices.
2. Choose an index per material and grade, published independently and accessible to both sides.
3. Record the base index value that the current price corresponds to.
4. Agree the review period and lag, for example quarterly using the previous quarter’s average.
5. Write the formula into the contract and agree that it applies in both directions.
6. Publish each adjustment with the index values used, so either side can reproduce it.

Related reading

See how the material line fits the whole cost in what is should-costing, or the raw-material negotiation service.