Buy-to-Let Mortgage Repayment Calculator
Calculate monthly debt service for a buy-to-let mortgage.
Property
Rental Property Cash Flow Calculator
Build rental cash flow from rent received after vacancy and the costs you enter. Repair reserves and loan principal affect available cash differently from operating expenses, so each is shown separately.
Your numbers
How the calculation works
Rental cash flow separates the property’s operating income from the cash absorbed by reserves and financing. That distinction matters because loan principal reduces available cash without being an operating expense in the NOI calculation.
Income = scheduled rent × (1 − vacancy) + other income. NOI = income − operating expenses. Cash flow = NOI − capital reserve − debt service.
Estimate income after vacancy
Reduce scheduled rent by the entered vacancy allowance, then add other property income. This produces the monthly income available before costs.
Calculate net operating income
Subtract operating expenses only. The capital reserve and financing remain outside this intermediate NOI figure.
Find distributable cash in the scenario
Deduct the separately supplied reserve and full debt service from NOI. Multiply the resulting monthly cash flow by twelve for the annual equivalent.
Worked example: Vacancy, reserves and debt service
Sample inputs demonstrate the method. They are not a forecast or product offer.
The example reduces €1,000 rent by 10% vacancy to €900 and adds €50 other income. Subtracting €200 operating costs gives €750 NOI. A €100 reserve and €400 debt payment leave €250 monthly cash flow, or €3,000 annually.
- Scheduled monthly rent
- 1000
- Vacancy allowance
- 10
- Other monthly property income
- 50
- Monthly operating expenses
- 200
- Monthly capital repair reserve
- 100
- Monthly debt payments including principal
- 400
Expected result
- Monthly cash flow
- €250.00
- Annual cash flow
- €3,000.00
- Monthly net operating income
- €750.00
Worked example: Full vacancy does not remove costs
Sample inputs demonstrate the method. They are not a forecast or product offer.
- Scheduled monthly rent
- 1000
- Vacancy allowance
- 100
- Other monthly property income
- 0
- Monthly operating expenses
- 200
- Monthly capital repair reserve
- 0
- Monthly debt payments including principal
- 300
Expected result
- Monthly cash flow
- -€500.00
- Monthly income after vacancy
- €0.00
Understanding your result
Positive cash flow indicates money remaining after these modelled deductions. Negative cash flow indicates an amount that must be funded from elsewhere under the scenario.
The annual figure assumes the same monthly position repeats. It is not a forecast of actual payment dates, capital repairs or seasonal vacancies, and it does not calculate personal rental tax.
Questions you might have
Why is cash flow different from profit?
Principal repayments reduce cash but are not an operating expense. Depreciation and tax rules can create further differences.
Choosing the right inputs
- Scheduled monthly rent
- Enter scheduled monthly rent before vacancy. The vacancy percentage reduces this rent; other monthly property income is added separately without that same automatic reduction.
- Monthly operating expenses
- Include recurring property operating expenses on a monthly basis. Keep the separate repair reserve and full debt payment out of this field.
- Monthly debt payments including principal
- Enter the complete monthly debt payment, including both interest and principal. This is a cash-flow deduction rather than an interest-only accounting expense.
Common mistakes to avoid
- Do not count the debt payment as an operating expense and subtract it again as debt service.
- A repair reserve is a cash allocation; including both the reserve and the same assumed repair cost can double count spending.
Assumptions to check
- Enter each cost in one category only; a reserve is a cash allocation rather than an incurred accounting expense.
Sources and method
Read our calculation and testing approach.