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Free UK Calculator

Buy-to-Let Mortgage Calculator

Compare interest-only vs repayment, see your rental yield, ICR stress test and post-tax cash flow — including the Section 24 impact most calculators miss.

Your numbers
Standard for most UK BTL mortgages. You repay the loan capital at the end of the term.
£
£
%
£

Monthly interest

£859

Loan amount

£187,500

75% LTV

Gross rental yield

6.72%

ICR @ 5.5% stress

163%

Target 145%

Annual cash flow (simplified)
Rental income£16,800
Mortgage payments− £10,313
Income tax (40% band, after 20% interest credit)− £4,658
Net cash flow£1,830

Higher-rate taxpayers are hit hardest by Section 24. Our Health Check flags whether incorporation or ownership restructuring could help.

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How this buy-to-let calculator works

Interest-only monthly cost is loan × annual rate ÷ 12. Repayment uses the standard amortisation formula over your chosen term. We also run the lender stress test most UK BTL lenders apply — your rent must cover at least 125% (basic rate) or 145% (higher rate) of mortgage interest at a stressed rate of 5.5%+. This is the Interest Coverage Ratio (ICR).

Section 24 and your real return

Since April 2020, individual landlords can no longer deduct mortgage interest from rental income. You receive a 20% basic-rate tax credit instead. For higher-rate taxpayers with leveraged portfolios, this can wipe out a large chunk of cash flow — which is why the calculator above shows tax-after-credit as a separate line.

This calculator is a planning tool, not tax advice. Your actual position depends on allowable expenses, ownership structure, other income and capital allowances. Run the Health Check for a personalised view.