What Is the Rent Increase Cap?
Definition
Rent Increase Cap: The highest increase allowed for a residential or commercial lease at renewal, usually tied to the change in a consumer price index over the previous rental year.
The rent increase cap is the highest rise allowed when a lease renews. Where a law sets one, it is usually tied to the change in a consumer price index over the previous rental year. The reader meets it at every renewal: the new rent cannot exceed the current rent raised by the cap, whatever the landlord asks.
Where it appears in the formulas
The rent increase calculator uses maximum new rent = current rent × (1 + CPI 12-month average change) and applies any fixed cap of the renewal period. The parties may always agree on a smaller increase.
Annual inflation is not the cap
The cap uses the CPI change by 12-month averages, not the annual CPI change. The two rates usually differ, so check which one a figure is before you use it.
In Türkiye
Under the Turkish Code of Obligations art. 344, the increase for a residential or roofed commercial lease cannot exceed the CPI change by 12-month averages of the previous rental year. TurkStat publishes the rate monthly; the rate of the month before renewal applies. Residential leases renewed from 11 June 2022 to 1 July 2024 could not rise more than 25% (Law 7409, extended by Law 7456); the calculator applies that cap in this period.