Rent Increase Calculator

How this is worked out

German tenants are protected by two separate limits, and a rent increase has to clear both. Whichever is lower is the one that governs.

The Kappungsgrenze (§558 BGB). Rent may not rise by more than 20% over three years. In areas designated by the state as a strained housing market — which covers Berlin, Munich, Hamburg, Frankfurt, Cologne and hundreds of other municipalities — that falls to 15%. The three years count backwards from the new rent taking effect, not from your last increase.

The ortsübliche Vergleichsmiete. Rent may never exceed the local comparable rent for a similar flat, whatever the cap would otherwise allow. Your city's Mietspiegel is the usual evidence. If comparable flats go for 1,150, your rent cannot be pushed past that even if the 15% cap would permit more.

Three procedural rules that invalidate a lot of increase letters:

• Twelve months must have passed since the last increase took effect
• The increase must be justified in writing, with evidence — a Mietspiegel reference, three comparable flats, or an expert opinion
• You have until the end of the second month after receiving it to agree. Silence is not agreement, and the landlord must sue if you do not consent

Modernisation is a separate track. After genuine improvement works, a landlord may add up to 8% of the cost per year, subject to its own caps. That sits outside the Kappungsgrenze and is not covered here.

A worked example

Rent 980 now, 950 three years ago, landlord proposes 1,180, Berlin, comparable rent 1,150.

• Cap: 15% of 950 = a limit of 1,092.50
• Comparable rent limit: 1,150
• The lower governs: 1,092.50
• Proposed increase is 24.2% over three years
• Too high — by 87.50 a month

The landlord may raise the rent to 1,092.50, not 1,180. Over a year that is 1,050 you would have paid unnecessarily.

Change one thing — the flat is outside a designated tight market — and the cap becomes 20%, a limit of 1,140. Still below the proposed 1,180, so still too high, but only by 40.

What this doesn't cover

• Everything here is Kaltmiete. Heating and service charges follow completely different rules and are not part of this.
• The tight-market designations are made by state ordinances that expire and are renewed, and they list specific municipalities. Check whether yours is currently designated rather than assuming.
• The Mietpreisbremse is a different rule — it caps the rent on a new tenancy at the comparable rent plus 10%, with exemptions for new-build and comprehensively modernised flats. It was extended to the end of 2029.
• Index-linked and stepped rents (Indexmiete, Staffelmiete) are agreed in the contract and follow their own rules; the Kappungsgrenze does not apply.
• This is general information about the statute, not legal advice. For a real dispute, a Mieterverein membership costs around 100 a year and includes legal help — usually the best money a German tenant can spend.

Common questions