Mortgage Repayment Calculator
Calculate your monthly mortgage repayments and see the total interest you'll pay over the life of your mortgage.
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20.0% deposit · 80.0% LTV
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Results are estimates only. Speak to a mortgage broker for personalised advice.
Repayment examples — 25 years, 4.5%, 20% deposit
Fixed 25-year repayment mortgage at 4.5% with a 20% deposit. Click any row to load it into the calculator.
| Property price | Loan amount | Monthly payment | Total interest | Total repaid |
|---|
How it's calculated
For a repayment mortgage, the monthly payment is calculated using the standard annuity formula: P × r(1+r)ⁿ / ((1+r)ⁿ − 1), where P is the loan amount, r is the monthly interest rate, and n is the total number of months.
LTV (loan-to-value) is the loan amount expressed as a percentage of the property value. A lower LTV typically means lower risk for the lender and access to better interest rates — many lenders reserve their best deals for LTVs below 60% or 75%.
For an interest-only mortgage, the monthly payment covers only the interest (loan × monthly rate). The full loan balance remains outstanding at the end of the term and must be repaid separately — for example through an investment or sale of the property.
Frequently asked questions
LTV stands for loan-to-value — it's the size of your mortgage as a percentage of the property's value. A lower LTV means lower risk for the lender, which usually means better interest rates. Most lenders require an LTV below 95%, and the best rates are typically available below 60–75% LTV.
A repayment mortgage gradually builds equity as you pay down the balance — at the end of the term, you own the property outright. Interest-only has lower monthly payments but you still owe the full loan amount at the end of the term. The vast majority of residential mortgages in the UK are repayment. Interest-only is more common for buy-to-let.
Even a 0.5% difference has a significant impact. On a £250,000 mortgage over 25 years, moving from 4.5% to 5.0% adds roughly £65 per month and around £20,000 in total interest. This is why remortgaging when a fixed rate ends — rather than rolling onto the standard variable rate — can save thousands over the life of your mortgage.