Wrong flat size in Germany: how m² affect rent and Nebenkosten

Many German service charges are split by floor area. If your flat is smaller than your landlord assumes, you pay too much every year, and possibly too much rent as well. Here is how living space is measured, and what you can do if the numbers do not match.

By Phil Holthaus & Johann Slawski, founders of nebify — Nebenkostenabrechnungen checked by people and software.

Last updated November 4, 2026

Key facts at a glance

Living space is usually measured under the Wohnflächenverordnung, not simply wall to wall.
Under sloped ceilings, areas below 2 m count half and below 1 m not at all. Balconies usually count a quarter.
For your Nebenkosten the real area counts, even if your contract says something else.
If the flat is more than 10 % smaller than agreed, you may reduce the rent.
A wrong area changes every item split by floor area: property tax, insurance, cleaning and often heating.

Tape measure on the wooden floor of an empty attic room

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Short answer

In Germany your Nebenkosten must be split by the real size of your flat, measured usually under the Wohnflächenverordnung. If the area in your statement is larger than your flat, every item split by floor area is too high. If the flat is more than 10 % smaller than agreed in your contract, you may also reduce the rent.

How living space is measured

„Die Grundflächen 1. von Räumen und Raumteilen mit einer lichten Höhe von mindestens zwei Metern sind vollständig, 2. von Räumen und Raumteilen mit einer lichten Höhe von mindestens einem Meter und weniger als zwei Metern sind zur Hälfte, […] 4. von Balkonen, Loggien, Dachgärten und Terrassen sind in der Regel zu einem Viertel, höchstens jedoch zur Hälfte anzurechnen.“

In English: “The floor areas 1. of rooms and parts of rooms with a clear height of at least two metres count fully, 2. of rooms and parts of rooms with a clear height of at least one metre and less than two metres count half, […] 4. of balconies, loggias, roof gardens and terraces count as a rule a quarter, but at most half.”

§ 4 WoFlV — our translation; only the German text is binding

What counts and how much

Ceiling 2 m or more: 100 %
Ceiling 1 to under 2 m: 50 %
Ceiling under 1 m: 0 %
Balcony, loggia, terrace: usually 25 %, at most 50 %
Cellar, storage outside the flat, laundry room, garage: not counted

The ordinance was written for subsidised housing, but according to the Federal Court of Justice it is usually applied to all rental flats unless something else was agreed or is locally customary (17 April 2019, VIII ZR 33/18).

Your Nebenkosten: the real area counts

Unless your contract says otherwise, service charges are split by floor area (§ 556a (1) BGB). The Federal Court of Justice decided that the real area counts, not the figure in your contract, and dropped the earlier 10 % tolerance (30 May 2018, VIII ZR 220/17). Even a small difference therefore matters.

Your area too high
Every item split by floor area is too high for you: property tax, insurance, cleaning, garden, often part of heating.
Total area too low
If the building's total area in the statement is smaller than real, every tenant's share is too high.

→ Living space calculator (German)

How to measure your flat

1
Measure each room
Length × width at floor level, from wall to wall. Note niches and bay windows separately.
2
Mark sloped ceilings
Measure where the ceiling is 1 m and 2 m high. Count the area between half, below 1 m nothing.
3
Add balcony and terrace
Usually a quarter of their area.
4
Leave out cellar and storage
Rooms outside the flat, the cellar and the garage are not living space.
5
Compare
With your contract and with the area in your Nebenkostenabrechnung.

Rent, rent increases and reclaiming money

If the flat is more than 10 % smaller than agreed, it counts as defective and the rent is reduced in proportion (BGH, 24 March 2004, VIII ZR 295/03).
For rent increases up to the local comparative rent, the real area counts (BGH, 18 November 2015, VIII ZR 266/14).
Overpaid service charges can be reclaimed with an objection within 12 months of each statement.

Ask your landlord for the area calculation before you act. If the figures differ clearly, a tenants' association (Mieterverein) can help with rent questions.

Area in your statement looks too big?

A few square metres more in the statement add up over every item and every year. Whether your area, the building's total area and the keys are right shows when the statement is checked against your contract. We do that and explain it in English.

Check my statement for free Full report from €24.90

The floor area is behind most items in a German utility bill. If you want to have your Nebenkostenabrechnung checked, we go through every item and send you an English summary with a ready-to-send letter to your landlord, for €24.90.

If you read German: our page Nebenkostenabrechnung prüfen lassen explains the same check in German.

FAQ: living space and flat size

How is living space calculated in Germany?

Usually under the Living Space Ordinance (Wohnflächenverordnung). Areas with a ceiling height of 2 m or more count fully, 1 to 2 m count half, under 1 m not at all. Balconies and terraces usually count a quarter, at most half. Cellars and storage rooms outside the flat do not count.

Which area is used for my Nebenkosten?

The real area, not the one in your contract. The Federal Court of Justice decided this in 2018 and dropped the earlier 10 % tolerance for service charges (30 May 2018, VIII ZR 220/17).

Can I reduce my rent if the flat is smaller than stated?

If the real area is more than 10 % smaller than agreed in the contract, the flat is considered defective and the rent is reduced accordingly (BGH, 24 March 2004, VIII ZR 295/03). You may also reclaim rent you overpaid, within the limitation period.

Does my balcony count as living space?

Yes, but usually only a quarter of its area, at most half (§ 4 No. 4 WoFlV).

How do I check my flat size?

Measure each room, note ceiling heights under sloped ceilings, and calculate under the rules above. If the result is clearly smaller, ask your landlord for the area calculation.

Does the area in your statement fit your flat?

Upload your statement to the free pre-check. You see in English whether the area and the split look plausible.

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Legal note: This guide gives general information and is not legal advice on your individual case. Whether an item in your statement is actually not allowed depends on your rental contract and the facts of your case. For legal questions, a tenants' association (Mieterverein) or a lawyer specialising in tenancy law (Fachanwalt für Mietrecht) can help you.

More guides in English

Sources: § 2 WoFlV · § 4 WoFlV · § 556a BGB; BGH, judgments of 24 Mar 2004 (VIII ZR 295/03), 18 Nov 2015 (VIII ZR 266/14), 30 May 2018 (VIII ZR 220/17) and 17 Apr 2019 (VIII ZR 33/18)