Wondering if the rent for your property is in line with the market? A deviation of just €75 per month means a loss of €9,000 over ten years. This article guides you through the precise calculation of the local comparable rent and protects you from costly mistakes.
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The topic briefly and concisely
The local comparative rent from the rent index is the most important data basis for any rent calculation.
Features such as a fitted kitchen (+12.6%) or full furnishings (+22.6%) significantly increase the rental value.
Legal regulations such as the rent control (maximum 10% above the comparative rent) and the cap limit (maximum 15-20% in 3 years) must be strictly observed.
Determining the correct rent is one of the most important decisions for property owners. Setting the rent too low reduces your return, while setting it too high can lead to vacancy and legal disputes. Therefore, a systematic approach is essential. With a precise rent calculator for your city and property size, you can determine the optimal basic rent based on the local rent index, the amenities, and legal regulations such as the rent control. This guide provides you with a data-driven method in 6 steps to realise the true value of your property and act in compliance with the law.
Step 1: Use the local rent index as a data basis
The basis for almost every rent calculator is the local comparative rent, which is depicted in the rent index of your municipality. Since a legal reform in 2021, all German cities with over 50,000 inhabitants are required to create and regularly update such a rent index. This document classifies rents by year of construction, apartment size, and location in a range or table form, resulting in a basic price per square meter.
A qualified rent index, which is created according to scientific principles, carries significant evidential weight in court and is the most reliable source. You will usually find the valid rent index on your city administration's website. The net cold rent indicated there is the starting point for all further calculations and adjustments. For initial guidance, you can access the rent index for your city online.
The correct application of this data foundation is the first step in conducting a well-founded rent price analysis and avoiding subjective estimates.
Step 2: Analyse value drivers and calculate premiums or discounts
No two apartments are identical, even within the same building. Therefore, the rent index only provides an average value, which must be adjusted for features that increase or decrease living value. These factors determine the exact positioning of your rent within the price range. A detailed location analysis is often the first step here.
The amenities are a crucial lever for the rent amount. A current analysis shows clear financial impacts:
Fitted kitchen: A modern fitted kitchen can increase the rent by an average of 12.6%.
Furnishing: Fully furnished apartments can achieve a surcharge of up to 22.6%.
Balcony/terrace: A balcony increases the rental value by about 2.7%, a garden by 3.6%.
Elevator: An elevator in the building justifies a slight surcharge of around 0.8%.
The energy condition, the state of modernization, and the quality of the floor coverings are also taken into account in the evaluation. These adjustments allow the rent price to be optimised beyond the mere average value.
Step 3: Check legal limits such as rent control
In areas with a tight housing market, the rent control limits the rent level for new leases. The rent here may be no more than 10% above the local comparative rent. Violations can lead to tenants demanding repayments. It is therefore essential to check the validity of the rent control for your location.
However, there are clearly defined exceptions to this rule. The most important are:
New construction: Apartments first used and rented after 1st October 2014 are exempt.
Comprehensive modernisation: If the investment in modernisation is at least one-third of the cost of a comparable new construction, the rent control does not apply.
Previous rent: If the previous tenant’s rent was already above the permissible limit, this amount may be maintained.
In addition to the rent control for new leases, the capping limit applies to existing tenancies. This restricts rent increases to a maximum of 20% (in some cities 15%) within three years. A calculator for modernisation surcharges helps to calculate permissible increases.
Step 4: From cold rent to warm rent – allocating additional costs correctly
The determined basic rent is only part of the total rental income. In addition, there are the apportionable operating costs, which are clearly regulated in the Ordinance on Operating Costs (BetrKV). Only ongoing costs may be passed on to the tenant, not one-off repair or administrative costs.
According to § 2 BetrKV, typical apportionable incidental costs include, among others:
Property tax
Costs for water supply and drainage
Heating and hot water costs
Lift operation
Street cleaning and waste disposal
Building cleaning and garden maintenance
Property and liability insurance
Costs for the caretaker
A transparent listing in the rental agreement is a prerequisite for apportionment. A precise calculator for rental income and ancillary costs helps you consider all permissible items and calculate a legally secure warm rent. This builds trust and avoids later conflicts over the ancillary cost settlement.
Step 5: Determine the Rent without a Rent Index
What to do if your community with fewer than 50,000 inhabitants does not offer a rent index? The Civil Code (§ 558a BGB) provides three alternative justifications in this case to determine or increase rent. Each method has its own requirements and a varying amount of effort involved.
Here are your options:
Expert opinion: A publicly appointed and sworn expert prepares a detailed analysis. This is the most legally secure but also the most expensive method, often costing over €500.
Comparable properties: You must specify at least three rented properties that are comparable in location, size, features, and year of construction. Listings from real estate portals are insufficient as they only show asking prices.
Rent databases: Some regions maintain rent databases jointly operated by interest groups. However, these are still relatively rare.
In these cases, it is especially important to clarify what rent you can ask for your house since the data basis is less standardised. Careful documentation is the key to success here.
Step 6: Use AI-powered rent calculators for a quick and data-driven assessment
Manually determining rental prices is complex and time-consuming. This is where digital tools provide a crucial advantage. Modern AI-driven valuation models (AVMs) analyse millions of data points in real time, including asking rents, actual closing rents, and detailed property characteristics. This allows you to receive an initial, objective assessment in seconds.
This technology does not replace the final, detailed analysis, but it significantly speeds up the process and provides a solid data foundation. Instead of laboriously working through spreadsheets, you can input parameters such as postcode, year of construction, and living area and receive a data-driven rent range. Such a rental yield calculator is ideal for an initial assessment, for example in the case of an inherited property.
Try it out for yourself and chat now for free with Auctoa ImmoGPT. It provides you with an initial price estimate and shows how AI can support you in property decisions. This data-driven approach minimises risks and maximises your potential.
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A professional rent calculator for your city and apartment size is more than just an online tool – it is a systematic process. It starts with the solid data foundation of the rent index, is refined by the analysis of location and amenities, and is secured by checking legal boundaries. Only the addition of apportionable ancillary costs leads to a complete and legally secure rent.
This careful calculation protects you from loss of yield and legal disputes. A data-based rent determination is not a matter of gut feeling, but the foundation for sustainable and successful real estate investment.
Additional useful links
The Statistische Bundesamt (Destatis) offers a table on rents and household net income in Germany.
Another table from the Statistische Bundesamt (Destatis) shows the housing stock in Germany.
Statista provides statistics on the monthly rental index for Germany.
The Wikipedia article explains the rent index as a tool for determining the local comparative rent.
The Bundesbank analyzes the development of prices for residential properties and rents in Germany in 2023.
The Deutsche Städtetag publishes a position paper on the rent index as a tool for dampening rent increases.
FAQ
Can I calculate the rent for my apartment myself?
Yes, you can calculate an estimate yourself. Use your city's rent index as a basis, adjust the value using lists of surcharges and discounts for the furnishings, and check the legal limits such as the rent control. However, for an exact, legally sound determination, it is advisable to use a digital tool or consult an expert.
How often is the rent index updated?
A simple rent index should be adjusted to market developments regularly, while a qualified rent index must be adjusted every two years. A complete new creation for qualified rent indexes is required every four years.
Which costs are not allowed to be passed on as additional costs?
Non-allocable are costs for administration (e.g., bank fees, tax advisor), maintenance and repair costs (e.g., replacement of a defective heating pump), as well as costs for rental loss or legal protection insurance of the landlord.
Does the rent control also apply to furnished apartments?
Yes, the rent control generally applies to furnished apartments as well. The landlord is only allowed to add a reasonable furnishing surcharge to the permissible base rent. Exceptions often apply only for rentals for temporary use.
What is the difference between Kaltmiete, Nettokaltmiete, and Warmmiete?
The net cold rent is the base rent for the living space. The cold rent (or gross cold rent) already includes some fixed operating costs. The warm rent is the total of cold rent and all variable operating costs, including heating and hot water. Typically, the net cold rent is used as the basis for the rental index.
Where can I find the rent index for my city?
You can usually find the official rent index on your city's or municipality's website, often in the citizen's or housing office. Tenant and owner associations such as Haus & Grund often provide the documents as well.
