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Construction price revision calculator: K coefficient and revised amount
Calculate the coefficient K = fixed part + Σ a × In / I0 and the revision amount of a situation, with your salary and material indices.
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Inputs
Indicative calculation from your inputs. Check contract terms and applicable rules before use. The example indices are fictitious: use the official indices and the formula of your contract.
Price revision
DZD 72,500.00
- Coefficient K
- 1.072500
- Revised amount excl. tax
- DZD 1,072,500.00
Fixed part + coefficients (must be 1)1.000000
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Calculation reference
Price revision adjusts the works amount to the change in costs. Multiply the period amount by K. K keeps a fixed part (often 0.15) and weights each index by its coefficient. A fall of the indices gives a negative revision.
Worked example
Situation 1,000,000 DZD excl. tax, fixed part 0.15. Salaries a = 0.35 (100 → 110), cement 0.25 (100 → 120), steel 0.25 (100 → 95): K = 0.15 + 0.385 + 0.300 + 0.2375 = 1.0725. Revised amount 1,072,500 DZD, revision 72,500 DZD. The example indices are fictitious.
Things to check
Do not use the index of the signature month if the contract sets another base month. Do not mix index bases. Check that the coefficients and the fixed part total 1.
Content reviewed on 04/10/2026
METHOD
An estimate you can verify
The formula and its coefficients come from the contract terms of your market. The fixed part and the coefficients must total 1. I₀ is the index of the base month set by the contract; Iₙ is the index of the works period. Algerian salary and material indices are homologated each quarter by ministerial order and published in the Official Journal. The tool contains no index: enter the official values. K is not rounded; if your contract sets a rounding, apply it.
Technical sourceFAQ
Where can I find the official indices?
The salary and material indices are homologated by order of the Ministry of Housing and published in the Official Journal. The public procurement portal lists them by quarter (source link on this page).
Revision or update of prices?
Revision applies during the execution of the contract. Update (actualisation) applies between the offer date and the start of works; it often uses the formula without the fixed part. For that case, enter a fixed part of 0 if your contract says so.