Buy to Let Affordability Calculator
Stress-tested rent vs mortgage for buy-to-let.
Calculate buy-to-let affordability using interest cover ratio (ICR) and stress-tested rate. Enter property price to see icr and stress-tested affordability.
What this tool does
Enter property price, rent, loan, rate. The tool shows ICR and stress-tested affordability.
Enter Values
Formula Used
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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.
250,000 property, 1,300 monthly rent, 75% LTV (187,500 loan) at 5.5% stress-tested to 7%: monthly interest 1,094, ICR 119%. BTL lenders typically require 125% ICR at 5.5-7% stressed rate. Below: unaffordable, above: lendable.
Run it with sensible defaults
Using property price of 250,000, monthly rent of 1,300, ltv of 75%, stress rate of 7%, the calculation works out to 118.86%. Nudge the inputs toward your own situation and the output recalculates instantly. The defaults are meant as a starting point, not a recommendation.
The levers in this calculation
The inputs — Property Price, Monthly Rent, LTV, Stress Rate, and ICR Required — do not pull with equal force. Not every input has equal weight. Flip one at a time toward extreme values to feel which ones move the needle most for your situation.
How the math works
Standard BTL ICR calculation. The working is transparent — you can verify every step yourself in the formula section below. No black box, no opaque "proprietary model".
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.
Related calculations worth running
Plans get firmer when you triangulate. Alongside this one, the rental yield calculator, the mortgage calculator, and the mortgage affordability calculator tend to come up in the same conversations. Running two or three together exposes inconsistencies in any single assumption — which is usually where the useful insight lives.
Buy-to-let affordability produces ratio figures based on the inputs provided.
Inputs
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
Standard BTL ICR calculation.
References
Frequently Asked Questions
What is ICR?
Why stress-test rates?
upper-rate taxpayers impact?
Property not yet let?
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