Rental Cash Flow Calculator with Worked Example
1. Short answer
The cash flow of a rental property is the rent that comes in less everything that goes out: operating costs, interest and principal. It is the only figure your bank account actually notices.
Cash flow = rent after voids − operating costs − interest − principal
The apartment used throughout these pages produces € 1,475 of rent a month and lands on a cash flow of − € 148 a month. The same property shows a gross yield of 5.37%. Both figures are correct; they simply measure different things.
2. What cash flow is, and what it is not
Cash flow is not a percentage but an amount. It tells you whether you receive money every month or have to top up, and that is a different question from whether the property is a good investment.
The difference from NOI sits entirely with the lender. NOI stops at operating costs and says nothing about financing; cash flow then deducts interest and principal. Two buyers of the same property therefore share an NOI and have completely different cash flows.
What it does not include:
- no capital growth: that touches your wealth, not your account
- no income tax or wealth tax
- no sale proceeds
- no one-off acquisition costs: those sit in your investment, not in your operation
Principal deserves a separate note. It is not a cost, because your wealth does not fall: the money moves from your account into equity in the property. But it does leave your account, which is why it belongs in cash flow. Leave it out and you credit yourself with money you cannot spend.
3. The formula, component by component
Rent. Not contracted rent but rent you actually collect. BRIX Calc handles voids and bad debt as percentages that reduce the rent rather than as separate cost lines. At a 5% void allowance the tool works with 95% of your monthly rent, and a bad-debt percentage multiplies down from there.
Operating costs. The rental calculator carries ten of them, and the most common mistake is mixing up the unit. Four are entered monthly, the rest annually:
| Item | Unit |
|---|---|
| Service charge (VvE) | per month |
| Utilities | per month |
| Maintenance reserve | per month |
| Insurance | per month |
| Property tax | per year |
| Ground rent (erfpacht) | per year |
| Management fee | per year, or as a percentage of rent |
| Your own operating items | per year |
Enter an annual figure in a monthly field and your cash flow is twelve times too low; the other way round, twelve times too high. That sounds like an error you would spot at once, but on a single line of a few hundred euros it rarely stands out.
Two of these items are specifically Dutch. VvE is the owners' association levy on an apartment, comparable to a service charge or HOA fee. Erfpacht is a ground lease under which the land stays with a third party, common in Amsterdam and a handful of other Dutch cities, and the annual canon is a real recurring cost that a freehold comparison does not have.
What BRIX Calc does. If the management fee is set as a percentage, the tool applies that percentage to collected rent rather than to contracted rent. Under a void assumption your management cost therefore falls too. That is realistic, but it also means a void scenario flatters your costs slightly compared with a fixed monthly amount.
Debt service. Interest and principal together. On an annuity loan that is the same amount every year with a shifting split between the two. Interest-only means interest alone. On a straight-line loan year one is the heaviest and the burden falls from there.
4. Worked example
The same renovated 75 m² apartment: € 1,475 base rent per month, € 6,626 of operating costs a year, financed with € 199,500 at 5.0% on a 30-year annuity. Figures in euros, on Dutch rules.
| Item | Per month | Per year |
|---|---|---|
| Base rent | € 1,475 | € 17,700 |
| Operating costs | − € 552 | − € 6,626 |
| NOI | € 923 | € 11,074 |
| Interest | − € 826 | − € 9,908 |
| Principal | − € 245 | − € 2,943 |
| Cash flow | − € 148 | − € 1,778 |
Cash flow per month = 1,475 − 552 − 826 − 245 = − € 148
| Metric | Value | What it means |
|---|---|---|
| Monthly cash flow, annuity | − € 148 | You top up every month |
| Monthly cash flow, interest-only | € 92 | Same property, same rate, no principal |
| Annual cash flow, annuity | − € 1,778 | What you must be able to carry each year |
| Principal per year | € 2,943 | Not a cost but an outflow: this becomes equity |
The gap between − € 148 and € 92 a month is nothing other than the principal. On the annuity you build € 2,943 of equity a year and pay € 1,778 a year out of pocket for it. Net, that is € 1,165 a year of wealth gained, but not a euro of it is spendable.
Sensitivity. Apply a 5% void allowance and collectable rent falls to € 1,401 a month, taking cash flow from − € 148 to − € 222. One vacant month in twenty costs € 74 a month, every month. That is why a void assumption is never a detail: it feeds through in full to the amount you have to find.
5. What counts as good cash flow?
Indicative ranges for Dutch residential investment in 2026 at roughly 70% financing and around 5% interest, not a published standard:
| Range per month | What it usually signals |
|---|---|
| negative | Common on an annuity loan in this market; you are steering on principal and growth |
| € 0 to € 100 | Barely positive; one void month a year still puts you under |
| € 100 to € 300 | Comfortable; room for maintenance that runs over |
| above € 300 | Check the assumptions, or accept that unusual risk is being taken |
Negative cash flow is not a disqualification, but it is an obligation. You must be able to carry it every month, including a year with a void and a failed boiler at the same time. So calculate not only the cash flow but also how many months you could sustain it without having to sell.
6. Three mistakes that distort the number
Forgetting the principal. That produces a cash flow your lender would not recognise. On this property it is € 245 a month: the difference between topping up and taking money out.
Using contracted rent. Twelve full months, every payment on time, is an assumption rather than a measurement. A 5% void allowance moves the answer here by € 74 a month.
Reading year one as the whole story. Rent indexes, costs index, and on an annuity the split between interest and principal shifts every year. On a straight-line loan the total burden falls year after year. A year-one cash flow is a starting position, not a verdict.
7. Run your own numbers
Enter your own figures above and monthly cash flow moves as you type, with and without principal. To see cash flow over ten or thirty years, with rent indexation, cost indexation and a rate reset, the BRIX Calc rental calculator models it year by year.
8. Frequently asked questions
Does principal belong in cash flow?
Yes. Principal is not a cost, but the money does leave your account, and cash flow measures exactly that. For a figure that counts principal as wealth building, use return on equity. For what is left to spend, cash flow including principal is the right number.
What is the difference between cash flow and NOI?
Financing. NOI is rent less operating costs and stops there; cash flow then deducts interest and principal. On this property NOI is € 11,074 positive and cash flow € 1,778 negative. The € 12,852 gap goes entirely to the lender.
Is tax included in cash flow?
No. BRIX Calc computes cash flow before income tax and before wealth tax, so the figure stays comparable between investors in different tax positions. To get your actual net position, deduct your own liability separately. The only tax the tool does put in the cash flow is a levy on sale, and that applies to some jurisdictions rather than the Dutch default.
Why is my cash flow negative while the yield is positive?
Because yield and cash flow measure different things. The 5.37% gross yield compares rent against the investment and ignores every cost and the lender. Cash flow deducts € 6,626 of operating costs and € 12,852 of debt service. Both are correct; gross yield simply says nothing about what you keep.
Does BRIX Calc use a real monthly schedule?
Not for the figure on the dashboard: that is year-one cash flow divided by twelve. The multi-year projection works per year, on an amortisation schedule that does follow the shifting split between interest and principal. For a rental property with a fixed monthly rent that is accurate enough; if your monthly outgoings vary sharply, check those separately.
How do voids enter the cash flow?
As a percentage that reduces the rent, not as a cost line. At a 5% void allowance BRIX Calc works with 95% of your monthly rent, and a bad-debt percentage multiplies down from there. These are two different risks that stack: a void is rent you miss because nobody lives there, bad debt is rent you miss while somebody does.