Indexmiete: Calculate Your VPI Increase (2026)
Updated 6/14/2026 · HausMaus Redaktion
With an Indexmiete (index-linked rent), your rent is tied to the Verbraucherpreisindex (VPI, the consumer price index) published by the Statistisches Bundesamt (Federal Statistical Office) under § 557b BGB. The new rent is: old rent × (current VPI ÷ base VPI). It may rise no sooner than one year after the last adjustment, must state the old and new index figures and the new rent in euros in Textform (text form), and is bound by neither the Kappungsgrenze nor the Mietspiegel. If any figure is missing, the increase is invalid.
What is an Indexmiete?
With an Indexmiete (index-linked rent), your rent is tied by contract to the Verbraucherpreisindex (VPI, the consumer price index) that the Statistisches Bundesamt (Federal Statistical Office) publishes monthly (§ 557b Abs. 1 BGB). When the VPI rises, the landlord may raise the rent in the same proportion – but only if the increase is declared correctly.
The most important point first: the increase does not happen automatically. The landlord must declare it to you in Textform (text form) and state the old and new index level plus the new rent in euros (§ 557b Abs. 3 BGB). If any of these is missing, the increase is invalid and, for now, you owe nothing extra.
How do I calculate the VPI increase?
The formula is simple:
new rent = old rent × (current VPI ÷ base VPI)
- old rent is the most recently agreed Nettokaltmiete (net cold rent, excluding Nebenkosten).
- base VPI is the index level at the last setting – at the start of the lease or the last adjustment.
- current VPI is the level at the time of the new increase.
Both values must use the same base year. The Statistisches Bundesamt currently calculates on the base 2020 = 100.
Worked example
| Item | Value |
|---|---|
| Old Nettokaltmiete | 900.00 € |
| Base VPI (last setting) | 119.8 |
| Current VPI | 125.2 |
| Index increase | 125.2 ÷ 119.8 = +4.51 % |
| New Nettokaltmiete | 900 € × (125.2 ÷ 119.8) = 940.57 € |
You work out the percentage index increase as: (current VPI ÷ base VPI × 100) − 100. In the example: 4.51 %. The landlord applies this percentage to the Nettokaltmiete – the Nebenkosten are not affected.
Check which VPI value applies directly at the Statistisches Bundesamt. Unless the contract says otherwise, the monthly value applies, not the annual average.
When can the rent rise – and from when do you pay?
Between two increases, the rent must stay unchanged for at least twelve months (§ 557b Abs. 2 Satz 1 BGB). If the landlord waits longer, they may claim the accumulated index rise in one step – that is permitted.
But you owe the increased rent only from the start of the second month after the declaration reaches you (§ 557b Abs. 3 Satz 3 BGB). If the declaration arrives in June, you pay from August. Unlike a Mieterhöhung (rent increase) under § 558 BGB, no consent from you is required.
What does not apply to an Indexmiete?
The Indexmiete follows its own logic. Several protections from ordinary rent- increase law expressly do not apply here:
| Rule | Applies to Indexmiete? |
|---|---|
| Kappungsgrenze 20 % / 15 % over 3 years (§ 558 Abs. 3 BGB) | No (§ 557b Abs. 2 Satz 3 BGB) |
| Binding to ortsübliche Vergleichsmiete / Mietspiegel | No |
| Tenant consent required | No |
| Mietpreisbremse for the starting rent (§ 556d BGB) | Yes – at the lease start |
During the term of an Indexmiete, an additional increase up to the Vergleichsmiete under § 558 BGB is excluded (§ 557b Abs. 2 Satz 3 BGB). A Modernisierungsumlage (modernisation surcharge) under § 559 BGB is only allowed where the landlord did not bring the modernisation about themselves (for example legally mandated measures).
Achtung: A planned reform (the "Mietrecht II" draft bill from the Bundesministerium der Justiz) would cap Indexmiete increases in strained housing markets at 3.5 % per year. As of June 2026 this is a draft and not yet in force. Check the current legal status before paying if your flat is in a designated area.
Common mistakes
- Accepting an increase with no index figures. Without the old and new index level and a euro amount, the declaration is formally invalid (§ 557b Abs. 3 BGB; BGH VIII ZR 291/16). You then owe nothing until it is declared correctly.
- Calculating on the gross rent. The index applies only to the Nettokaltmiete, not to the Nebenkosten.
- Mixing different base years. The old and new VPI must use the same base year (currently 2020 = 100), or the calculation is wrong.
- Paying immediately on receipt. The new rent is owed only from the second month onward (§ 557b Abs. 3 Satz 3 BGB).
- Tolerating increases that are too frequent. At least twelve months must lie between two adjustments (§ 557b Abs. 2 Satz 1 BGB).
HausMaus makes this easier
HausMaus helps you check an Indexmiete increase calmly before you pay. In the rent-increase decision helper you enter the declared increase and see the reason, the earliest effective date and the deadline at a glance – then accept or record your objection directly. Through the lease analysis you upload your Mietvertrag (tenancy contract) and get the Indexmiete clause and the § 557b BGB form requirements explained. All tenant features in HausMaus are free. Wohnen, geregelt. (Home, handled.)
Frequently asked questions
How do I calculate my Indexmiete?
The new rent is: old rent × (current VPI ÷ base VPI). The base VPI is the Verbraucherpreisindex of the Statistisches Bundesamt at the time of the last setting, the current VPI the level at the increase – both on the base 2020 = 100. Example: 900 € × (125.2 ÷ 119.8) = 940.57 €. What matters is the percentage change of the index, applied to the most recently agreed Nettokaltmiete (net cold rent) under § 557b Abs. 2 BGB.
How often can the Indexmiete be increased?
At most once a year. After each adjustment the rent must stay unchanged for at least twelve months (§ 557b Abs. 2 Satz 1 BGB). An increase has no retroactive effect, but if the landlord has not raised the rent for longer than a year, they may claim the accumulated index rise in one step.
From when do I have to pay the increased Indexmiete?
Only from the start of the second month after the increase declaration reaches you (§ 557b Abs. 3 Satz 3 BGB). If the declaration arrives in June, you pay the new rent from August. You owe nothing extra before then, even if the index rose long ago.
Does the Kappungsgrenze or the Mietspiegel apply to an Indexmiete?
No. The Kappungsgrenze (cap on rent increases) of 20 % over three years under § 558 Abs. 3 BGB expressly does not apply to the Indexmiete (§ 557b Abs. 2 Satz 3 BGB). There is also no binding to the ortsübliche Vergleichsmiete (local comparative rent) or the Mietspiegel (rent index table). Only the VPI matters. A 3.5 % per-year cap in strained housing markets is, however, planned from 2026 (see below).
What must the increase declaration contain?
It must be in Textform (text form, email is enough) and state three things: the VPI change that has occurred (old and new index level) and the new rent or the increase as a euro amount (§ 557b Abs. 3 Satz 2 and 3 BGB). If any of these is missing, the increase is invalid (BGH, judgment of 22 November 2017, Az. VIII ZR 291/16).
Can the Indexmiete also go down?
Yes. With the Indexmiete the rent changes with the VPI – so in both directions (§ 557b Abs. 1 BGB). If the index falls, the rent can fall accordingly. A clause allowing only increases puts the tenant at a one-sided disadvantage; any agreement deviating to the tenant's detriment is invalid (§ 557b Abs. 5 BGB).
Sources
This guide is based on the statute text and official sources. You can read the cited paragraphs in the original here: