Buy-to-Let Mortgage Calculator

How this calculator works

Enter the rent, the price, your deposit and the product rate. The stress rate field pre-fills to the higher of your product rate plus 2 percentage points or 5.5% — the two figures most commonly published as the floor lenders stress-test against — and you can overwrite it once a broker gives you a specific lender's own number. Pick the cover ratio: 125% is the figure most often quoted for basic-rate individual landlords and limited companies; up to 145% is common for higher-rate individual taxpayers, because Section 24 leaves them keeping less of each pound of rent after tax (our Section 24 page covers why). The calculator works out the largest loan this rent supports at that stress rate and cover ratio, caps it at a 75% loan-to-value ceiling against the price you entered (a common but not universal lender limit), and shows the deposit, monthly interest, yield and rent-cover percentage that follow.

Reading each output

• Maximum loan the rent supports — work backwards from this if the rent is fixed and you want to know the biggest mortgage it will justify.
• Required deposit — price minus that maximum loan (or the 75% LTV cap, if that binds first). Compare it with the deposit you actually have.
• Gross yield is annual rent over price; net yield here only deducts mortgage interest — not insurance, management fees, voids or maintenance — so it will read higher than your true return. Our rental yield calculator is the fuller version if you want running costs included too.
• Rent cover achieved is the same ICR mechanic the lender runs, at the loan actually being used. It should sit at or above your chosen cover ratio by construction — if the LTV cap binds before the rent cover does, you'll see cover above the minimum, which is a sign the deposit, not the rent, is the limiting factor.

Different question, same convention: the dedicated stress test

This calculator answers “what can this rent support?” If you already have a specific loan amount in mind and want a pass/fail check against it, the buy-to-let mortgage stress test runs the same ICR mechanic the other way round — loan in, verdict out — and is the better tool once you're comparing a real offer.

Portfolio landlords: a stricter process, not a stricter number

Once you hold four or more mortgaged buy-to-let properties, the underwriting changes shape rather than the ICR number itself. Lenders apply the PRA's specialist buy-to-let underwriting expectations (SS13/16) across the whole background portfolio — aggregate rental cover, total borrowing, a property schedule, sometimes a business plan — on every new application, not just the property being mortgaged. That narrows the panel of lenders willing to deal with you and adds paperwork; it is not a documented higher ICR figure we could verify from a primary source, so we don't print one. Our buy-to-let mortgage rates explained guide covers this and the limited-company question in full.

Before you apply

Check the stamp duty surcharge on the purchase, what the rent does to your rental income tax, and whether a company purchase changes the borrowing and tax picture enough to be worth the extra running costs.

Bank of England / PRA: SS13/16 Underwriting standards for buy-to-let mortgage contracts, read live 12 September 2026. The 5.5%/pay+2% stress-rate convention, the 125%–145% cover ratios and the 75% LTV cap are commonly published lender criteria, not figures fixed by the supervisory statement itself, and are presented as such — the same convention already used on our buy-to-let mortgage stress test. The four-or-more-property “portfolio landlord” threshold is the market's own reading of SS13/16's specialist-underwriting expectation, not a sentence we could verify verbatim on the live SS13/16 page.