Buy-to-Let Stress Test Calculator
Check whether your rental income passes lender stress tests. Most buy-to-let lenders require rent to cover 125-145% of the mortgage at a stress-tested interest rate.
Property & mortgage
Interest rates & criteria
The rate you expect to pay
Typically 5.5% — check with your lender
Typically 125% (basic rate) or 145% (higher rate)
Stress test result
FAILS stress test
Rental coverage at stress rate: 140% (need 145%)
Monthly payment (actual rate)
£703.13
at 4.5%
Monthly payment (stress rate)
£859.38
at 5.5%
Minimum rent to pass
£1,246/mo
£14,953/year
Max borrowing at this rent
£180,564
at 5.5% stress rate
Buy-to-let stress testing explained
What is a stress test? Lenders check whether your rental income would still cover mortgage payments if interest rates rise. They use a "stress rate" (typically 5.5%) regardless of your actual rate.
Rental coverage ratio: Lenders require rental income to exceed the stressed mortgage payment by a margin. This is typically 125% for basic rate taxpayers or 145% for higher rate taxpayers. Some lenders use different ratios.
Why 125% vs 145%? Since Section 24 (mortgage interest restriction), higher rate taxpayers face a bigger tax bill on rental income. Lenders require higher coverage to account for this.
Interest-only: Most buy-to-let mortgages are interest-only. This calculator uses interest-only payments. If you have a repayment mortgage, your actual payments will be higher but the stress test typically still uses interest-only.
Use our mortgage calculator to see full repayment schedules, or our tax calculator to understand Section 24's impact.
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