UK Mortgage Calculator 2024-25

How do UK mortgage lenders calculate affordability?

Most UK mortgage lenders use a loan-to-income (LTI) multiple to assess affordability. The standard maximum is 4.5 times your annual gross income — for example, if you earn £50,000, the maximum mortgage is typically £225,000. Some lenders offer up to 5 or 5.5 times income for professionals or high earners. Lenders also conduct a stress test to ensure you could afford the mortgage if rates rose by 3 percentage points. In addition to the LTI multiple, they assess your credit score, outstanding debts, monthly commitments, and whether you have dependants. The Mortgage Market Review (MMR) rules require lenders to conduct thorough affordability assessments rather than simply relying on income multiples.

What is LTV and why does it matter for mortgage rates?

Loan-to-value (LTV) is the ratio of your mortgage to the property value, expressed as a percentage. A 10% deposit means an LTV of 90%; a 25% deposit means an LTV of 75%. LTV is crucial because it determines the mortgage rate you are offered. Lenders price risk: lower LTV borrowers (larger deposits) are offered lower interest rates because there is more equity to protect the lender if the borrower defaults. The best mortgage rates are typically available at 60% LTV or below. Most lenders require a minimum 5% deposit (95% LTV), but rates at 95% LTV are significantly higher than at 75% or 60%. Paying down your mortgage over time reduces your LTV, and remortgaging at a lower LTV can secure better rates.

Should I choose a repayment or interest-only mortgage?

A repayment mortgage means you pay off both the interest and a portion of the capital each month, so your mortgage is fully paid off at the end of the term. This is the most common type of residential mortgage in the UK. An interest-only mortgage means you only pay the interest each month — the full capital remains outstanding and must be repaid at the end of the term (usually by selling the property or using savings/investments). Interest-only mortgages have much lower monthly payments but result in significantly higher total costs and leave you with the capital debt intact. Most residential lenders now require a credible repayment vehicle (such as an ISA or pension) before offering interest-only mortgages. Interest-only is more common for buy-to-let investors who can offset the interest against rental income.

How does a fixed vs tracker mortgage affect my payments?

Fixed-rate mortgages lock your interest rate for a set period (typically 2, 3, or 5 years), meaning your monthly payment stays the same regardless of Bank of England base rate changes. This provides certainty and protection against rate rises. Tracker mortgages follow the Bank of England base rate plus a set margin — if the base rate changes, your payment changes accordingly. Standard Variable Rate (SVR) is what you revert to after a fixed or tracker period ends, and is usually higher than initial product rates. In the 2024/25 environment with base rates elevated, many borrowers are choosing 5-year fixed rates for long-term certainty. Always compare the total cost over the initial period plus any early repayment charges (ERCs) rather than just the monthly payment.