How UK Mortgages Work
A UK mortgage is a loan secured against a property, regulated by the Financial Conduct Authority (FCA). You borrow a percentage of the property price (the loan-to-value, or LTV), and repay it over a set term — typically 25 years — with interest. The deposit is the portion you pay upfront, usually 5% to 25% of the price. The bigger your deposit, the lower your LTV, and the better the interest rate you'll qualify for.
Most UK mortgages are "repayment" mortgages: each monthly payment covers that month's interest plus a portion of the capital, so the balance falls steadily and the mortgage is fully repaid at the end of the term. "Interest-only" mortgages are also available (mainly for buy-to-let), where you pay only interest each month and the full loan is due at the end — but these are riskier and harder to qualify for.
Fixed vs Variable Rates
UK mortgages are typically fixed for an initial period — 2, 3, 5, or 10 years — after which the rate reverts to the lender's Standard Variable Rate (SVR), which is usually 2-4% higher. Most borrowers remortgage to a new fixed deal at the end of the initial period to avoid the SVR. A 5-year fix at 5.09% gives you certainty for 5 years; a 2-year fix at 5.49% is cheaper initially but you'll need to remortgage sooner. The Bank of England base rate (currently 4.75%) influences but doesn't directly set mortgage rates — lenders price based on funding costs, competition, and risk appetite.
Overpaying: The Biggest Money-Saver
Overpaying your mortgage is one of the highest-return, lowest-risk financial moves available in the UK. Every pound you overpay goes straight to reducing your capital, saving you interest at your mortgage rate for the entire remaining term. On a £250,000 mortgage at 5.09% over 25 years, overpaying £200/month saves about £28,000 in interest and cuts about 5 years off the term. That's a guaranteed, tax-free return that no ISA or savings account can match.
Most lenders allow overpayments of up to 10% of the outstanding balance per year without penalty. Check your mortgage terms — exceeding the limit can trigger Early Repayment Charges (ERCs), typically 1-5% of the overpayment. See our blog post on whether you should overpay your mortgage for the full math.
Loan-to-Value (LTV) and Why It Matters
Your LTV is the loan amount as a percentage of the property price. A £200,000 loan on a £250,000 property is an 80% LTV. Lower LTVs get better rates: at 60% LTV you might pay 4.5%, at 80% LTV you might pay 5.2%, at 90% LTV you might pay 5.8%. A bigger deposit doesn't just reduce the loan — it also reduces the rate on the loan you do take, compounding the saving. If you can stretch to a 20% deposit instead of 10%, you save on both the principal and the rate.
More UK Finance Tools
- Mortgage Affordability Calculator — how much you could borrow based on your income.
- Stamp Duty Calculator — SDLT with first-time buyer relief and additional-property surcharge.
- Personal Loan Calculator — unsecured loan repayments with representative APR.
- ISA Calculator — tax-free savings growth within the £20,000 annual allowance.
Disclaimer: Finance Atlas is not regulated by the FCA. This calculator provides estimates for educational purposes only and does not constitute financial advice or a mortgage offer. Always consult a qualified, FCA-regulated mortgage adviser.