Buy to Let Mortgage Calculator
Estimate your monthly mortgage cost, rental stress test, loan-to-value (LTV), and expected cash flow.
For information only. Results are estimates and not financial advice.
What this buy to let mortgage rates calculator helps you do
Buy-to-let investing is heavily numbers-driven. A deal that looks strong at first glance can become weak once mortgage costs, lender stress tests, and fees are included. This calculator gives you a fast way to check whether the property is likely to stack up before you speak to a broker or lender.
It combines the core numbers most landlords care about:
- Monthly mortgage payment (interest-only or repayment)
- LTV (loan-to-value)
- Gross rental yield
- ICR (interest coverage ratio) at pay rate and stress rate
- Minimum rent needed to pass stress testing
- Estimated monthly cash flow before non-mortgage costs
How buy to let mortgage rates work
Buy-to-let rates are influenced by base rates, swap rates, lender risk appetite, your deposit size, your personal tax position, and the property type. Most buy-to-let products are either fixed-rate deals (e.g., 2-year or 5-year fixes) or trackers that move with an index.
Interest-only vs repayment
- Interest-only: Lower monthly payment, but the original loan balance remains outstanding at the end of the term.
- Repayment: Higher monthly payment, but you gradually pay down the loan principal.
Many landlords choose interest-only for cash flow flexibility, then use rent growth, overpayments, savings, or sale proceeds as their long-term repayment strategy.
Inputs explained
Property value and deposit
These determine your loan size and LTV. In many cases, better rates are available at lower LTV bands (for example 60% or 75%).
Interest rate and term
The rate drives your monthly cost. The term mostly affects repayment mortgages; for interest-only, term impacts total interest paid over time.
Rent, stress rate, and ICR
Lenders commonly test affordability using a stress rate and required ICR. If expected rent is too low, borrowing may be reduced even if the property seems profitable in real life.
How to interpret your results
- LTV: Lower usually means lower risk and potentially stronger rates.
- Gross yield: Useful for quick comparisons, but not the same as net profit.
- ICR at stress rate: A key lender metric; below requirement can block the loan.
- Cash flow: Positive cash flow is good, but remember management, maintenance, voids, insurance, tax, and compliance costs.
Example use case
Suppose you analyze a £250,000 property with a £62,500 deposit, 5.25% mortgage rate, and rent of £1,300 per month. The calculator immediately shows whether:
- the mortgage payment is covered with a safety margin,
- the rent likely passes a 125% ICR at a 6.5% stress test, and
- your monthly surplus is enough after allowing for real-world operating costs.
Tips to improve your buy to let mortgage rate
- Increase your deposit to reduce LTV.
- Strengthen your landlord profile (experience, clean credit, low existing debt).
- Compare fees + rates together, not rate alone.
- Consider fixing for longer when rate volatility is high.
- Use a specialist broker for complex property types or limited-company structures.
Final thought
A buy-to-let property should be tested from multiple angles: finance, risk, and resilience. Use this calculator to pressure-test each deal quickly, then validate with a full broker illustration and accountant-led tax review before committing.