Rent Increase Calculator: Check the Capping Limit and Comparative Rent

§ 558 of the German Civil Code (Bürgerliches Gesetzbuch, BGB) allows landlords to ask the tenant to consent to a rent increase up to the local comparative rent (ortsübliche Vergleichsmiete). This is the most common form of rent increase during an ongoing tenancy. The requirement is that the current rent is below the local comparative rent and that the formal requirements are met.

Every increase is capped by two independent upper limits: (1) the local comparative rent and (2) the capping limit (Kappungsgrenze). The rent may only be raised up to the lower of the two values. The landlord must make the increase request in text form and justify it with one of the legally permitted methods (rent index, appraisal, comparable apartments or rent database).

Important: rent increases under § 559 BGB (modernisation), § 557a BGB (graduated rent, Staffelmiete) and § 557b BGB (index-linked rent, Indexmiete) are subject to their own rules and are not covered by this calculator. Our calculator focuses exclusively on the increase up to the local comparative rent under § 558 BGB.

The capping limit (Kappungsgrenze) under § 558 (3) BGB limits how much the rent may rise within 3 years. Regardless of how high the comparative rent is, the rent may rise by at most 20% within 3 years. In areas with tight housing markets, the state governments can reduce this limit to 15% by regulation.

As of March 2026, 14 of the 16 federal states have issued a capping-limit regulation. Around 700 municipalities are affected by the reduced 15% limit. Only Saarland and Sachsen-Anhalt have not introduced a reduction; there the regular 20% capping limit still applies.

The basis for the calculation is the base rent(Ausgangsmiete): the rent that applied exactly 3 years before the planned increase date. All increases during this period are added up. If the tenancy began within the last 3 years, the starting rent serves as the basis. Modernisation surcharges under § 559 BGB do not count towards the capping limit.

Example: with a base rent of €620 and a 15% capping limit, the rent may rise by at most €93 over 3 years (€620 × 15%). If it has already been raised by €80, €13 of room remains.

The table below shows the current status of the capping-limit regulations for all 16 federal states (as of March 2026).

The local comparative rent (ortsübliche Vergleichsmiete) is the central reference value for every rent increase under § 558 BGB. It describes the average rent for comparable apartments in the municipality. The landlord must justify the rent requested with one of the four legally permitted methods under § 558a (2) BGB:

• Rent index (Mietspiegel): drawn up by the municipality or an interest group. If a qualified rent index exists, the landlord must refer to it.
• Rent database (Mietdatenbank): a continuously maintained collection of rent data recognised by the municipality or the relevant interest groups.
• Expert appraisal: an appraisal by a publicly appointed and sworn expert.
• Comparable apartments: naming at least 3 comparable apartments with the corresponding rent.

A qualified rent index (qualifizierter Mietspiegel) is prepared according to scientific principles and recognised as qualified by the municipality or the relevant interest groups (§ 558d BGB). Currently 205 municipalities in Germany have a rent index, 124 of them qualified. You can find your city's rent index on the city administration's website or at your local tenants' association (Mieterverein).

A rent increase under § 558 BGB is subject to binding deadlines that both landlords and tenants should be aware of:

• Blocking period (Sperrfrist): at least 12 months must lie between two rent-increase requests (§ 558 (1) sentence 2 BGB).
• Waiting period (Wartefrist): at the point the increase takes effect, the rent must have been unchanged for at least 15 months (§ 558 (1) sentence 1 BGB).
• Consent deadline: the tenant has until the end of the second calendar month after receiving the request to consent (§ 558b (2) BGB).
• Taking effect: the new rent applies from the beginning of the third calendar month after receipt of the request.
• Lawsuit deadline: if the tenant does not consent, the landlord has a further 3 months to sue for consent (§ 558b (2) BGB). If the deadline is missed, the increase request lapses.
• Special termination right: the tenant may give special notice until the end of the second month after receipt of the request (§ 561 BGB). The termination takes effect at the end of the month after next.

Example: service on 1 April 2026: the consent deadline ends on 30 June 2026, the new rent takes effect on 1 July 2026, and the lawsuit deadline ends on 30 September 2026.

Have you received a rent-increase request from your landlord? Check these 9 points before you consent:

1. Text form? The request must be in text form (letter, email, fax). A verbal demand is invalid.
2. Addressed to all tenants? Where there are several tenants, the request must be addressed to all of them.
3. Justification provided? The landlord must justify the increase with a rent index, appraisal, rent database or comparable apartments.
4. Qualified rent index referenced? If your municipality has a qualified rent index, the landlord must refer to it.
5. Blocking period observed? At least 12 months must have passed since the last increase request.
6. 15-month waiting period observed? At the point the increase takes effect, the rent must have been unchanged for at least 15 months.
7. Comparative rent not exceeded? The rent requested may not exceed the local comparative rent.
8. Capping limit not exceeded? The sum of all increases over the last 3 years may not exceed 20% (or 15% in tight markets).
9. No graduated or index-linked rent? With graduated or index-linked rent contracts, an increase under § 558 BGB is excluded.

If even a single point is not met, the rent increase is formally invalid. In that case you are not obliged to consent. When in doubt, seek advice from your local tenants' association (Mieterverein).

Besides the rent increase up to the comparative rent (§ 558 BGB), there are other forms that follow their own rules:

• Graduated rent (Staffelmiete, § 557a BGB): the rent increases are contractually agreed in fixed steps. The capping limit and the comparative rent are irrelevant. During the term of the graduated rent, an increase under § 558 BGB is excluded.
• Index-linked rent (Indexmiete, § 557b BGB): the rent is tied to the consumer price index of the Federal Statistical Office. Here too, neither the capping limit nor the comparative rent applies. § 558 BGB is excluded.
• Modernisation surcharge (§ 559 BGB): after energy-efficiency or other modernisation, the landlord may raise the annual rent by at most 8% of the costs incurred. Absolute upper limits apply: at most €3/m² over 6 years (€2/m² where the base rent is below €7/m²). Modernisation surcharges do not count towards the capping limit.

Our calculator is not suitable for any of these special cases. It calculates only the maximum rent increase under § 558 BGB.

The rent increase is only part of the bigger picture. Depending on whether you are a landlord or a tenant, these tools can help you further:

• Landlords who want to check their yield: Rental Yield Calculator
• Tenants who want to check their living area: Living Area Calculator
• Owners under renovation pressure: Energy Efficiency Quick Check
• Tenants considering buying: Rent vs. Buy Calculator and Budget Calculator