Mortgage Repayment Calculator UK 2026
Use our free mortgage calculator to work out your monthly repayments, total interest costs, and see a year-by-year amortization breakdown. Simply enter your loan amount, interest rate, and mortgage term to get instant results.
Amortization Summary (Yearly)
| Year | Opening Balance | Annual Payment | Interest Paid | Principal Paid | Closing Balance |
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How Mortgage Repayments Work in the UK
When you take out a repayment mortgage in the UK, each monthly payment consists of two components: interest charged on the outstanding balance and a portion that reduces the loan principal. In the early years of your mortgage, a larger proportion of each payment goes toward interest because your outstanding balance is at its highest. As you progress through the term and the balance decreases, more of each payment goes toward paying down the principal. This is known as amortization, and our calculator above shows this progression year by year.
The standard formula used to calculate monthly mortgage repayments is M = P[r(1+r)^n]/[(1+r)^n-1], where P is the principal loan amount, r is the monthly interest rate (annual rate divided by 12), and n is the total number of monthly payments (years multiplied by 12). This produces a fixed monthly payment that remains constant throughout the mortgage term, assuming a fixed interest rate. Variable rate mortgages will see this payment change whenever the rate adjusts.
Understanding Interest on Your Mortgage
Mortgage interest in the UK is typically calculated on a daily or monthly basis against your outstanding balance. With a repayment mortgage, the balance decreases with each payment, which means the total interest you pay over the term is significantly less than simply multiplying the annual interest rate by the loan amount and the number of years. For example, a £250,000 mortgage at 4.5% over 25 years results in monthly payments of approximately £1,390 and total interest of around £167,000 — considerably less than 4.5% of £250,000 multiplied by 25 years (which would be £281,250).
The interest rate you secure has an enormous impact on your overall costs. Even a seemingly small difference of 0.25% can add up to thousands of pounds over the life of the loan. On a £250,000 mortgage over 25 years, the difference between 4.25% and 4.50% is approximately £4,200 in additional interest. This is why shopping around for the best rate, using a mortgage broker, and timing your application well can yield significant savings. Our calculator helps you model these scenarios by adjusting the interest rate slider and comparing results.
Fixed Rate vs Variable Rate Impact
With a fixed-rate mortgage, the interest rate and monthly payment remain constant for the agreed period, typically two, three, five, or ten years. This provides certainty for budgeting and protects you from rate increases. When the fixed period ends, you typically move onto the lender's Standard Variable Rate (SVR), which is almost always higher. Most borrowers remortgage to a new fixed deal before their current one expires to avoid the SVR penalty.
Variable rate mortgages, including tracker mortgages that follow the Bank of England base rate plus a set margin, will see payments fluctuate. A tracker at base rate plus 1% would currently give you a rate of around 4.5-5.0%, but this could rise or fall with Bank of England decisions. While tracker rates can be lower than equivalent fixed rates, they carry the risk of payment increases that could strain your budget. Use this calculator to model different rate scenarios and see how payment changes affect your total costs.
Choosing the Right Mortgage Term
The mortgage term — the number of years over which you repay the loan — has a dramatic effect on both your monthly payments and total cost. A shorter term means higher monthly payments but significantly less total interest paid. A longer term reduces monthly payments but increases the total amount you repay over the life of the mortgage. The standard UK mortgage term has been 25 years for decades, but many lenders now offer terms up to 35 or even 40 years, particularly for first-time buyers who need to reduce monthly outgoings to pass affordability checks.
Consider the impact: a £250,000 mortgage at 4.5% over 20 years costs approximately £1,582 per month with total interest of £129,700. The same mortgage over 30 years costs £1,267 per month but total interest rises to £206,000. Over 35 years, monthly payments drop to £1,181 but total interest climbs to £246,000. The difference between a 20-year and 35-year term is over £116,000 in additional interest. Where your budget allows, choosing a shorter term or making overpayments is one of the most effective ways to reduce the cost of your mortgage.
Tips for Getting the Best Mortgage Deal
- Improve your credit score before applying — pay off credit cards, ensure you are on the electoral roll, and check for errors on your credit file with Experian, Equifax, and TransUnion.
- Save the largest deposit possible — crossing key LTV thresholds (90%, 85%, 80%, 75%, 60%) unlocks progressively better rates.
- Compare the total cost, not just the interest rate — factor in arrangement fees, valuation fees, and any cashback or free legals offered.
- Consider using a mortgage broker — they have access to deals not available directly and can navigate complex situations such as self-employment or adverse credit.
- Start the process early — get a mortgage in principle (also called a Decision in Principle or Agreement in Principle) before house hunting so you know your budget and can move quickly.