What does the "one-third rule" mean when it comes to rent?

The financial rule of thumb: analysis and facts

How is the one-third rule calculated for rent?

Calculating the one-third rule for rent seems simple at first glance, but it has its pitfalls in the details. Your gross annual income usually serves as the basis.

The formula is: Gross annual income : 12 : 3 = Maximum monthly rent

A calculation example illustrates the one-third rule for rent : If you earn 6,000 Swiss francs gross per month, your apartment should cost no more than 2,000 francs according to the one-third rule . It's important to note that the one-third rule always refers to the gross rent, meaning the rent including all utilities (advance payments for heating, water, building maintenance). Anyone who only uses the net rent for the one-third rule is deceiving themselves and risks exceeding their budget.

Why landlords insist on the one-third rule for rent

For property management companies, the one-third rule for rent is a risk minimization tool. They want to ensure that the rent is affordable for you in the long term. Even if you were willing to spend 50 percent of your salary on a penthouse apartment, a reputable management company will usually reject you.

Why? Because experience shows that ignoring the one-third rule for rent increases the risk of payment defaults. Unforeseen expenses – car repairs, dental bills, or back taxes – can then immediately lead to late rent payments. The one-third rule for rent is therefore not a form of harassment, but rather a safeguard for solvency.

Gross vs. Net: A common misconception

A critical point regarding the one-third rule for rent is the distinction between gross and net income. Property management companies almost always calculate the one-third rule for rent based on gross income (income before deductions).

For you personally, however, it's safer to interpret the one-third rule for rent more conservatively and base it on your net income (what actually ends up in your bank account). This is because social security contributions, pension contributions, and taxes are deducted from your gross income. If you strictly apply the one-third rule to your gross income, you might find yourself short of money at the end of the month in cantons with high tax burdens. Using the one-third rule based on your net income gives you more financial flexibility for leisure and savings.

The one-third rule for rent for couples and shared apartments

one-third rule for rent changes . In this case, the combined household income is added together.

If both partners earn 4,500 francs each, the household income is 9,000 francs. According to the one-third rule for rent, you could afford an apartment for up to 3,000 francs. However, joint and several liability applies here: both parties are liable for the entire rent. The one-third rule for rent only works in this scenario as long as both incomes are being paid . Separations are a common reason why the one-third rule for rent suddenly no longer applies and apartments have to be vacated.

Exceptions to the rule: Low and high earners

The one-third rule for rent is a rule of thumb, not a law of nature. It depends on income bracket. postpones the relevance .​

• Low incomes: For those earning very little, the one-third rule for rent is often difficult to adhere to, as affordable housing is scarce. At the same time, exceeding the one-third rule for rent is even riskier, since the remaining money is barely enough for food and health insurance.
• High incomes: Landlords sometimes take a more relaxed view of the one-third rule for rent when dealing with very high earners . Someone earning 15,000 francs could theoretically spend 40 percent on housing and still have enough to live on. Nevertheless, institutional investors usually adhere strictly to the one-third rule for rent in order to meet their compliance guidelines.

Special considerations for newcomers (expats)

For newcomers, the one-third rule for rent often comes as a surprise, as in metropolises like London or New York, 50 percent of income is typically allocated to housing. In Switzerland, however, the one-third rule for rent is culturally and economically ingrained. Furthermore, those subject to withholding tax should be aware that since the tax is deducted directly from their salary, their net pay will be lower. Therefore, the one-third rule for rent should be calculated with particular care to avoid cash flow problems.

Additional costs and inflation

In times of rising energy prices, the one-third rule for rent is becoming increasingly relevant. Utility costs (advance payments) are often set too low. If you push the one-third rule to the absolute limit, a hefty utility bill at the end of the year can easily break your budget. Experts therefore advise including a buffer when applying the one-third rule for rent and allocating only 25 to 30 percent of your income for it.

Conclusion

The one-third rule for rent is more than just a mathematical exercise; it's the anchor of your financial stability. It protects you from overextending yourself and is also key to being seen as a serious candidate by landlords. Ignoring the one-third rule for rent risks rejections during the application process and everyday financial stress.

Especially in expensive cities, adhering to the one-third rule for rent often requires compromises in terms of apartment size or location. However, this sacrifice pays off in terms of quality of life and financial security. Calculate honestly, include all additional costs, and use the one-third rule for rent as a strict upper limit, not as a target.

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Glossary

• The one-third rule for rent: A financial rule of thumb that states that a maximum of one-third of gross income should be spent on gross rent.
• Gross rent: The rent including monthly advance payments for utilities. This is the relevant figure for the one-third rule regarding rent .
• Affordability: The assessment of whether a tenant or buyer can afford the ongoing costs of a property in the long term.
• Joint and several liability: In the case of multiple tenants (e.g., couples, shared apartments), all are jointly liable for the entire rent, which is taken into account when calculating the one-third rule for rent .
• Advance payments: Monthly prepayments for ancillary costs (heating, water), which are settled at the end of the year.