Buy-to-Let Mortgage Calculator

Calculate BTL mortgage payments (interest-only and repayment). Check rental coverage stress test.

Last updated: April 2026 · Source: FCA — Mortgages overview

£
£
£

Interest Only

£859.38/month

Repayment

£1,151.41/month

LTV

75.00%

Rental Coverage

128.00%

Meets 125%

Monthly Cashflow

£240.63

Mortgage

£187,500.00

BTL mortgages typically require 25%+ deposit. Lenders stress-test at 125-145% rental coverage on interest-only. Additional property SDLT surcharge (5%) applies.

Disclaimer

This calculator is provided for informational purposes only and should not be considered as financial or tax advice. All calculations are performed locally in your browser — no personal data is collected or sent to our servers. Rates and thresholds are sourced from HMRC and GOV.UK and are updated for the current tax year. Always verify results with HMRC or consult a qualified professional before making financial decisions.

How It Works

Buy-to-let mortgages differ from residential mortgages in several ways. Most are interest-only, meaning monthly payments cover only the interest and the full capital balance is due at the end. Lenders typically require a rental coverage ratio of 125-145%, meaning the rental income must exceed the mortgage payment by that margin at a stress-tested interest rate.

Minimum deposits for buy-to-let are usually 25% of the property value, giving a maximum LTV of 75%. Some lenders offer up to 80% LTV at higher rates. Interest rates are typically 0.5-1.5% higher than equivalent residential rates. Affordability is assessed primarily on rental income rather than personal income, though most lenders also require a minimum personal income of £25,000.

This calculator models both interest-only and repayment buy-to-let mortgages. Enter the property price, deposit, rental income and interest rate to see monthly payments and the rental coverage ratio. It flags whether the rental income meets the typical 145% lender requirement at a stress rate of 5.5%.

Example: £250,000 property, 25% deposit, £1,100/month rent

  1. Mortgage: £187,500 at 75% LTV
  2. Interest-only at 5.2%: £187,500 × 5.2% ÷ 12 = £812.50/month
  3. Rental coverage: £1,100 ÷ £812.50 = 135%
  4. Stress test at 5.5%: £859.38/month, coverage = 128%
  5. Warning: below 145% threshold — some lenders may decline

Source: FCA — Mortgages overview

Frequently Asked Questions

What does the Buy-to-Let Mortgage Calculator do?
Calculate BTL mortgage payments (interest-only and repayment). Check rental coverage stress test. All calculations are performed in your browser using official UK rates and thresholds.
Is this based on current interest rates?
You can enter any interest rate to model different scenarios. Check the Bank of England base rate and current mortgage deals from lenders for the latest rates.
Should I get professional advice?
This calculator provides estimates for guidance only. For a formal mortgage offer, speak to a mortgage broker or lender who can assess your full circumstances and provide personalised advice.