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# How to calculate the rented portion when only part of your main residence is rented out?

If you're renting out only part of your main residence (e.g., a room or a floor), you need to calculate what percentage of the total living space is actually rented. This helps determine the taxable rental income and how to fairly allocate deductible expenses.

**Rented portion (%) = (Rented area in m² / Total area of the property in m²) × 100**

**Example:**
Total area of your home: 120 m²
Area rented out (e.g., a floor or a room): 30 m²

**Calculation:**
30 m² / 120 m² = 0.25 → that means 25 % of the property is rented

**In this example:**
* 25 % of your home is considered rented → this part generates taxable income
* 75 % is still your main residence → this part is not subject to rental tax

This also means that 25 % of the building-related expenses (e.g. insurance, interest, maintenance) may be claimed as rental-related deductions, if they are eligible.