Estimate the loan, LTV, monthly mortgage payment, rental coverage and cash surplus for a UK rental property.
The cash surplus shown is rent minus the calculated mortgage payment only. It excludes tax, voids, repairs, insurance, management fees and other costs.
How to use the Buy-to-Let Mortgage Calculator
Enter the purchase price, cash deposit, interest rate, term and expected rent. Choose interest-only or capital repayment and a rental coverage target. The result compares the rent with the calculated mortgage payment, but it is not a lender decision.
What the calculator works out
| Result | Calculation |
|---|---|
| Mortgage amount | Property price − deposit |
| Loan to value | Mortgage ÷ property price × 100 |
| Interest-only payment | Mortgage × annual rate ÷ 12 |
| Repayment payment | Monthly amortisation over the selected term |
| Rental coverage | Monthly rent ÷ monthly mortgage payment × 100 |
Rental coverage and lender assessments
Lenders commonly compare expected rent with a stressed mortgage interest payment. Their interest coverage ratio, stress rate, borrower tax position and acceptable property types differ. The 125% and 145% options are planning scenarios, not universal approval thresholds.
Interest-only versus repayment
Most buy-to-let mortgages are interest-only, so the monthly payment does not reduce the capital balance. A repayment mortgage normally costs more each month but repays capital over the term. An interest-only borrower needs a credible plan to repay the full balance.
Related property calculators
Compare a residential repayment using the United Kingdom Mortgage Calculator. Check borrowing percentage with the Loan to Value Calculator, test extra payments with the Mortgage Overpayment Calculator UK, or explore part-buying with the Shared Ownership Calculator UK. Browse all tools on the United Kingdom Calculator homepage.
MoneyHelper’s buy-to-let mortgage guide explains that expected rent often needs to cover roughly 125% to 145% of mortgage repayments and that many buy-to-let loans are interest-only.
Frequently asked questions
How much deposit do I need for buy-to-let?
Requirements vary by lender and borrower. Use the deposit input to test different LTV scenarios and confirm actual criteria with a mortgage adviser or lender.
What is rental coverage?
It compares monthly rent with the mortgage payment. A result of 145% means rent is 1.45 times the calculated payment.
Does passing 125% or 145% guarantee approval?
No. Lenders may use a different stress rate, coverage ratio and wider eligibility checks.
Does an interest-only payment reduce the balance?
No. It covers interest only, so the original capital normally remains due at the end of the term.
Are landlord costs included in the surplus?
No. The surplus excludes tax, repairs, voids, insurance, service charges, management fees and other ownership costs.