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Rent reduction calculator for Swiss leases

The mortgage reference rate has been 1.25 % since 02.09.2025. If your rent was set when the rate was higher, you can request a reduction. Enter two numbers and see how much – including the inflation and cost offsets your landlord may claim.

How the calculation works

Swiss rent law ties residential rents to the mortgage reference rate published quarterly by the Federal Housing Office (BWO). When the rate falls, the rent may be reduced by the official pass-through rate: for rates below 5 %, 2.91 % per 0.25 percentage point (Art. 13 VMWG). The steps are not simply added up – the official table applies (0.50 point = 5.66 %, 0.75 point = 8.26 %, 1.00 point = 10.71 %).

The landlord may offset two things against that reduction:

• Inflation: 40 % of the increase in the Swiss consumer price index (LIK) since your rent was last set (Art. 16 VMWG).
• General cost increases for maintenance, operations and fees (Art. 12 VMWG). Without proof, practice accepts a flat rate – the calculator uses 0.5 % per year. Landlords can claim more only with evidence.

That is why the date matters: it tells us which reference rate applied back then and how much inflation has accrued since. If you know the rate from your lease, enter it – it takes precedence.

Worked example

Net rent CHF 2'000, set in December 2023 at a reference rate of 1.75 %. The rate is now 1.25 %, a drop of 0.50 point → 5.66 % reduction before offsets. The landlord deducts 40 % of inflation since December 2023 and the flat cost increase for the elapsed years; what remains is your claim. Try it above with your own numbers.

What happens after the calculation

1. Send a written request to your landlord – before the notice period to the next termination date begins. See the request template.
2. The landlord has 30 days to answer. If they refuse or don't answer, you can go to the free conciliation authority.
3. The lower rent applies from the next termination date. Check the dates for your canton under notice dates by canton.

We can prepare the complete request from your lease, have it signed digitally by all tenants and send it by registered mail – for a one-time CHF 39. The calculation is always free.

When the calculator does not apply

Indexed leases (rent tied to the CPI, fixed term of at least 5 years) and graduated leases (fixed steps, at least 3 years) do not follow the reference rate during the fixed term – see indexed and graduated leases. Commercial premises, subsidised housing and luxury flats are also excluded. Landlords may raise further objections such as neighbourhood rents or insufficient yield; see landlord objections.

The calculator gives a technical estimate based on the official BWO pass-through table and the FSO consumer price index. It is not legal advice.