Rent increase calculator: how much more do you have to pay?
Have the landlord’s letter at hand: current rent, rent demanded and the date it arrived are enough for a first check.
Checked by Radif Partners · Editorial policy · Method
Maximum lawful new rent
€820
€40 more than allowed
| Local reference rent | €6.65/m² |
| Reference rent for your floor area | €412.30 |
| Range in the rent index | 5.77–8.74 €/m² |
| Rent brake | applies until 31 December 2029 |
| Increase cap | 15 % in three years |
| Cap limit | €943 |
| Binding limit | reference rent |
| Consent by | 31 December 2026 |
| New rent from | 1 January 2027 |
You only have to agree up to the lawful amount; partial consent is possible. Without consent the landlord must sue within three further months (Section 558b BGB).
How we calculateDuring a tenancy a German landlord may ask you to agree to a higher rent under Section 558 of the Civil Code (BGB), but only up to the local reference rent (ortsübliche Vergleichsmiete) and only within the increase cap (Kappungsgrenze): at most 20 per cent above the rent of three years earlier, or 15 per cent where the state has lowered the cap. Increases after modernisation and changes in service charges are left out of that count. On top of that, the rent must have stayed unchanged for 15 months when the increase takes effect. The calculator takes the cap from your state's ordinance and works out the reference rent itself for Berlin, Hamburg and Dortmund. A Hamburg example: a 1972 flat of 70 m² in a normal location, index median €6.76 per square metre. With rent of €680, €620 three years ago and €820 demanded, at most €680.00 is lawful, because the cap only allows €713.00. You have until 31 December 2026 to agree; the new rent applies from 1 January 2027.
What the calculator checks
It works through the conditions of Section 558 BGB in order. First the amount: the new rent may not exceed the local reference rent nor rise by more than the cap above the rent of three years earlier. Which cap applies in your municipality comes from your state's cap ordinance, checked for the day your letter arrived. Then timing: a demand may come no earlier than 12 months after the last increase, and the new rent takes effect only once the old one has applied for 15 months.
Last, the deadlines in Section 558b BGB: you have until the end of the second calendar month after receipt, and you owe the higher rent from the start of the third. If you do not agree, the landlord can sue for consent within three more months; after that his demand lapses.
The Hamburg example
| Check | Amount |
|---|---|
| Reference rent, Hamburg index 2025, field K3 | €6.76 per m² |
| Reference-rent limit for 70 m² | €473.20 |
| Cap limit: €620 plus 15 per cent | €713.00 |
| demanded | €820.00 |
| lawful | €680.00 |
| agree by | 31 December 2026 |
| new rent from | 1 January 2027 |
Hamburg has lowered the cap to 15 per cent across the city; in a municipality without an ordinance it would be 20 per cent, and here the reference rent would then have set the limit. The pages on the increase cap and on rent increases explain the background. An increase after modernisation follows its own procedure, covered by the modernisation calculator; with an index-linked rent an increase under Section 558 is ruled out altogether.