FinToolSuite

Rental Yield vs Mortgage Cost Calculator

Updated April 17, 2026 · Mortgage · Educational use only ·

Does rental income cover the mortgage?

Compare monthly rental income against mortgage cost to see buy-to-let cashflow position. Enter mortgage payment and running costs for an instant result.

What this tool does

Enter monthly rent, monthly mortgage payment, and monthly running costs. The tool shows cashflow position.


Enter Values

Formula Used
Monthly rent
Monthly mortgage
Monthly running costs

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Disclaimer

Results are estimates for educational purposes only. They do not constitute financial advice. Consult a qualified professional before making financial decisions.

Buy-to-let only works if rent covers mortgage plus costs. 1,500 rent minus 900 mortgage minus 300 running costs (letting fees, maintenance, insurance) = 300/month surplus. Positive cashflow is the minimum; anything negative relies on capital appreciation to be worthwhile.

A worked example

Try the defaults: monthly rent of 1,500, monthly mortgage payment of 900, monthly running costs of 300. The tool returns 300.00. You can adjust any input and the result updates as you type — no submit button, no reload. That's the real power here: seeing how sensitive the output is to one or two assumptions.

What moves the number most

The result responds to Monthly Rent, Monthly Mortgage Payment, and Monthly Running Costs. Two inputs usually tip the answer one way or the other. Identify which ones matter most by flipping each value past a round threshold and watching whether the winning option changes.

The formula behind this

Simple monthly cashflow calculation. Does not include void periods (vacancy) which typically run 5-10% — apply that adjustment if planning long-term. Everything the calculator does is shown in the formula box below, so you can check the math against your own spreadsheet if you want.

Stress-testing the plan

Run the calculation at your current rate, then run it again at a rate 2–3 percentage points higher. That's roughly what a product reset could bring at renewal, and it's a useful check on whether you can afford the mortgage in a higher-rate world, not just today's.

What this doesn't capture

The figure excludes arrangement fees, valuation costs, legal fees, insurance, and any early-repayment charges — those can add several thousand to the headline cost. Rate changes at renewal for fixed-term deals will shift the picture further. Use this for the core interest/principal math and add the other costs on top.

Example Scenario

Rental cashflow produces a monthly figure based on the inputs provided.

Inputs

Monthly Rent:1,500 £
Monthly Mortgage Payment:900 £
Monthly Running Costs:300 £
Expected Result£300.00

This example uses typical values for illustration. Adjust the inputs above to match a specific situation and see how the result changes.

Sources & Methodology

Methodology

Simple monthly cashflow calculation. Does not include void periods (vacancy) which typically run 5-10% — apply that adjustment if planning long-term.

Frequently Asked Questions

What's positive enough?
200-400/month surplus per property is common target. Below that, voids and maintenance surprises eat the buffer.
Does this include tax?
No. Rental income is taxable in most jurisdictions. After-tax surplus is typically 60-80% of the pre-tax figure for upper-rate taxpayers.
Typical running costs?
15-25% of rent for managed lets (letting fees + maintenance + insurance). Self-managed saves 8-12% but adds time commitment.
Void periods to plan for?
5-10% vacancy is typical across a long holding period. Budget for one empty month every 10-15 months.

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