Michal Smetana · Updated 03/10/2026

How the Výnosometr calculator works

What the calculator computes, which data it uses, how the traffic-light rating works and where its limits are. No formulas, plain language.

Výnosometr shows how much a buy-to-let flat in Czechia earns or costs you each month, and the return on your own money over the whole holding period including the sale. It uses Czech mortgage terms, taxes and costs as of 2026.

In three steps

1. Enter the flat. City, price, size, your deposit and how you will let it (long-term or short-term via Airbnb). You can also paste a listing and the calculator picks out the price, size and other details.
2. The calculator fills in the rest. By city it sets typical rent or nightly rate, owners' association fees, property tax, insurance, maintenance, mortgage rate and tax regime. Filled-in values are marked and you can overwrite each of them.
3. See the result. Monthly cash flow, return on your equity, the traffic-light rating and specific changes that would make the flat a good investment.

What the calculator computes

It goes through the whole holding period year by year, not just one "average" month. It includes:

• Income: rent with vacancy and tenant changes; for Airbnb occupancy, nightly rate, cleaning fee, ramp-up and platform fees.
• Costs: owners' association fees and repair fund, property tax, insurance, maintenance, management or your own time; for Airbnb cleaning, linen, supplies and furnishing renewal.
• Mortgage: payments, interest, fixation and the rate after it, bank fees and the Czech National Bank limits for buy-to-let mortgages.
• Taxes: Czech income tax on rent or business income, flat-rate versus actual expenses with depreciation, for Airbnb social and health insurance and VAT. It also handles spouses' joint property and ownership via a company.
• Sale: price growth, selling costs, the remaining loan and tax on the sale (exempt after 10 years).
• Comparison with an ETF: what the same money would have earned in an equity fund over the same period.

Terms like IRR, LTV or DSCR are explained in the glossary.

How we rate an investment

A return figure alone is not enough, because an optimistic price growth assumption pushes it up easily. The rating therefore combines three tests:

• Return: the annual return on your own money after tax (IRR). At least 8% for green.
• Resilience: the return in a pessimistic scenario (higher rate after fixation, slower price growth, lower occupancy). At least 4% for green.
• Cost coverage: whether rent covers interest, running costs and tax. Topping up principal is fine, topping up interest is not.

Green means a good investment, orange an investment with caveats, red a weak investment. Details in how to read the results.

What the calculator does not do

• It does not know the specific flat: condition, layout, building or street. Defaults are city averages.
• It does not predict the future. Price growth, rates after fixation and rents are assumptions you can change.
• Taxes are simplified for typical situations. For binding decisions consult a Czech tax adviser.

Data sources

Default values are based on these public sources. Market data as of 30 September 2026, updated quarterly; legislation yearly. We use the figures as calculation inputs and do not republish their content.

Our own calculations in the rental yield index are available under CC BY 4.0 with attribution to "Výnosometr (vynosometr.cz)".