How is a rent reduction calculated?
Rent reduction in Germany is calculated based on the gross warm rent (Bruttowarmmiete) – the base rent plus all utilities and heating costs. This was established by the Federal Court of Justice (BGH) in its landmark ruling of July 20, 2005 (Az. VIII ZR 347/04).
The formula is:
Example: With a gross rent of €900 and mold in the bedroom (reduction rate 15%) over 20 days:
Rent reduction takes effect automatically by law (§ 536 BGB) – you do not need to apply for it. However, you must first notify your landlord of the defect in writing (Mängelanzeige).
Rent reduction table: How much for which defect?
The amount of rent reduction depends on the type and severity of the defect. The following values are based on published court rulings and serve as guidance:
Mold in the apartment
5–100%Minor mold in one room: 5–10%. Mold in kitchen, bathroom, and bedroom: 20–50%. Apartment uninhabitable: up to 100%.
Heating works partially: 5–20%. Complete failure in winter: 50–100%. No hot water: 10–30%.
Damp walls or ceiling: 5–15%. Drying equipment in use: 50–80%. Apartment uninhabitable: 100%.
Occasional construction noise: 5–15%. Continuous daytime noise: 15–30%. Extreme noise day and night: 30–50%.
Power outage
5–100%Individual outlets defective: 5–10%. Complete power outage: up to 100%.
Pests / vermin
5–50%Ants or silverfish: 5–10%. Mice or rats: 10–30%. Cockroaches: up to 50%.
Elevator defective
5–20%Depending on floor and duration: 5–20%. Particularly relevant from the 4th floor up.
View the complete rent reduction table with all court rulings →
Frequently asked questions about rent reduction
Is rent reduction calculated from gross or net rent?
Rent reduction is always calculated from the gross warm rent – base rent plus all utilities including heating costs. This was decided by the BGH in its 2005 ruling (Az. VIII ZR 347/04).
Do I need to announce the rent reduction?
No, rent reduction takes effect by law. However, you must notify your landlord of the defect (Mängelanzeige). Only from that point on may you reduce the rent. A 14-day deadline for repair is standard.
Can I reduce rent retroactively?
In principle yes, but only from the point when you notified the landlord of the defect. Tip: Pay rent under reservation of reclaiming the amount, then you can demand the difference back later.
How much percent rent reduction for mold?
It depends on the extent: Minor mold in one room typically justifies 5–10%. Mold in multiple rooms: 20–50%. If the apartment is uninhabitable, the reduction can be up to 100%. Use our calculator above for an estimate.
Can I reduce rent without a lawyer?
Yes. For out-of-court claims, you do not need a lawyer. What matters is a proper defect notification, the right reduction rate, and correct calculation. Our calculator and letter generator help you with that.
What happens if I reduce too much?
If you withhold too much rent, the landlord could terminate the lease for non-payment. That is why it is important to follow court rulings and calculate the reduction correctly. When in doubt, pay under reservation and reclaim the amount later.
Rent reduction per day or per month?
Rent reduction is calculated on a daily basis. If the defect exists for only part of the month, the monthly rent is divided by 30 and multiplied by the number of affected days.
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