Calculate the change in an index
Pick a start month to see how far the Domestic PPI sub-indices and CPI have moved since, with the In/Io ratio the price adjustment uses. Data from TÜİK. No sign-up.
Ratio = In / Io
Change = (In / Io − 1) × 100
- The base month is the tender month
- The current month is the application month
- CPI for labour
Index change
Pick your tender month as the start. Leave the end month empty and each index is compared with its own latest month on our site.
| Index | Change | Ratio (In/Io) | October 2024 | End |
|---|---|---|---|---|
| Domestic PPI General (2003=100) | +61.81% | 1.618114 | 3,707.10 | 5,998.51October 2026 |
| C Manufacturing | +63.76% | 1.637609 | 3,573.02 | 5,851.21October 2026 |
| 23 Non-metallic mineral products | +49.65% | 1.496545 | 4,357.79 | 6,521.63October 2026 |
| 23.5 Cement, lime and plaster | +51.52% | 1.515172 | 4,395.33 | 6,659.68October 2026 |
| 23.6 Concrete, cement and plaster articles | +41.44% | 1.414382 | 4,599.76 | 6,505.82October 2026 |
| 24 Basic metals | +51.59% | 1.515851 | 5,402.22 | 8,188.96October 2026 |
| 24.1 Iron and steel | +43.90% | 1.43902 | 4,912.21 | 7,068.77October 2026 |
| 19 Coke and refined petroleum products | +168.78% | 2.687757 | 6,509.93 | 17,497.11October 2026 |
| 16 Wood and cork products | +64.27% | 1.642734 | 2,761.78 | 4,536.87October 2026 |
| 28 Machinery and equipment | +60.46% | 1.60458 | 2,572.66 | 4,128.04October 2026 |
| 35 Electricity and gas | +35.58% | 1.35576 | 2,974.28 | 4,032.41October 2026 |
| CPI General (labour) | +72.42% | 1.7242 | 2,598.91 | 4,481.04October 2026 |
Source: TÜİK.
October 2024 – October 2026
- Ratio (In/Io)
- 1.618114
In a price adjustment each input's ratio is multiplied by its coefficient in the contract; one index's change is only part of the sum.
Calculate the price adjustment- Indices arrive every month by themselves; each payment's price adjustment is worked out with the latest ones.
- The price adjustment lands on the payment cover, which you can save as a PDF.
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For information only. The indices are published by TÜİK; the Domestic PPI is taken from TÜİK, the CPI (2003=100) from the CBRT's EVDS. The CPI's 2026 figures are TÜİK's 2025=100 series linked to the 2003=100 base (the CBRT's EVDS).
How an index change is calculated
An index's change between two months is its value in the end month divided by its value in the start month. It is the same ratio the price adjustment uses for each input.
Ratio = In / Io
Change = (In / Io − 1) × 100
Io is the start month's index and In the end month's. The ratio is worked to 12 places, as in the price-adjustment calculator; the table shows 6.
Worth knowing
- The base month is the tender month
- In a price adjustment the base index belongs to the month the tender date falls in (Principles art. 4/1-ı).
- The current month is the application month
- The current index belongs to the application month (art. 4/1-ç): the month the work programme says the work should be done (art. 4/1-i).
- CPI for labour
- Labour uses the general figure of TÜİK's Consumer Price Index (2003=100) (Principles art. 5/4-a). It is not a producer price index.
- Series can end in different months
- A series' latest month on our site can trail the others. With no end month, each series is compared at its own latest month.
- A price adjustment is weighted
- Each ratio is multiplied by its coefficient in the contract and summed into Pn; the amount is F = An × 0.90 × (Pn − 1).
- Missing figures are never zero
- No ratio is shown for a month our site has no figure for, or one before a series starts; the row says why.
What this tool does not calculate
It does not work out a price adjustment amount; that needs the contract's coefficients and the work amount. Fuel prices are not in this table.
The indices are published by TÜİK. The Domestic PPI series are taken from TÜİK, the CPI General (2003=100) from the CBRT's EVDS. Since January 2026 TÜİK has published the CPI on a 2025=100 base. The 2026 figures in the site's CPI General (2003=100) series are the 2025=100 series linked to the 2003=100 base (the CBRT's EVDS). The In/Io ratio comes out the same on both bases, apart from a very small rounding difference. For information only.
About index change
- Price IndicesDomestic PPI sub-indices and CPI, monthly tables since 2012.
- Price Adjustment CalculatorPrice adjustment with the official formula, from Domestic PPI and CPI.
- Progress Payment Deductions CalculatorThe cover's VAT, every deduction from a) to k) and the net amount paid to the contractor, on one sheet.
- Quantity Takeoff CalculatorRebar, concrete, formwork and excavation takeoffs: a measurement sheet with deductions, exact totals and a copy for Excel.
- Work Experience Update CalculatorWhat a work experience certificate counts for in the tender you enter, with the right Domestic PPI months for its kind.
- Stamp Duty CalculatorThe 9.48 per mille stamp duty on a progress payment, with the yearly cap.
- VAT Withholding CalculatorThe VAT withheld on a progress payment, at the communiqué's rate for the work type.
- Withholding Tax CalculatorWithholding tax on a multi-year construction payment, at the rate for the work type and payment month.
- Performance Bond CalculatorThe performance bond on a bid, with the below-limit 9% rule and additional bonds.
- Minimum Labour CalculatorThe minimum labour to declare for the SGK clearance, the shortfall and its estimated premium.
- Advance Payment CalculatorThe advance, its 30% or one-third cap, the recovery rate and what comes off each progress payment.
- Work Increase CalculatorThe work increase room left under the 20% (unit price) or 10% (lump sum) limit.
- Completion Compensation Calculator5% of the shortfall when work ends below 80%, updated to the acceptance month by Domestic PPI.
- Delay Penalty CalculatorThe delay penalty from the first contract price, daily rate and days late, with the 15% cap.
- Work Duration CalculatorCompletion date from the site handover, days late, final acceptance and payment deadlines.
- Fuel PricesEPDK monthly averages by fuel type, for the fuel coefficient of a price adjustment.
- Minimum WageThe labour index of service procurement: gross, net and the employer's cost in public tenders, period by period.
Stop tracking indices by hand every month
Enter the coefficients once; indices arrive every month and the price adjustment lands on the payment by itself.