Calculating CBS rent increase: step-by-step with example

Step 1: choose the right series

Check your rental contract for which index applies. For ROZ contracts, this is the CPI, 'alle huishoudens' (all households) series. Do not use the HICP or a derived series, unless the contract mentions it.

Step 2: determine the two months

Count back four months from the indexation date (new figure) and sixteen months back (old figure). Example for 1 January 2026: September 2025 and September 2024.

Step 3: pay attention to the base year

The CBS (Statistics Netherlands) occasionally recalibrates the index to a new base year. If your contract mentions an older base year, use the CBS linking factor or the CBS calculation tool, which does this automatically. The percentage does not change because of this, but the index figure does.

Step 4: calculate

Divide the new figure by the old one and multiply by the current rent. In the rent indexation calculator, you fill in the two figures and immediately see the new rent per year and per month.

Common mistakes

• Using the month of the indexation date itself instead of four months prior.
• Using two different base years interchangeably.
• Indexing the rent over the VAT instead of the rent exclusive of VAT.
• Indexing service charges: these are settled separately.

Sources

• CBS StatLine, Consumer prices; price index: cbs.nl