Mortgage calculator
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Your monthly mortgage payment depends on three things: how much you borrow, the interest rate, and the length of the term. On a repayment mortgage, each monthly payment covers that month’s interest plus a slice of the original loan. Early in the term, most of your payment goes toward interest. Over time, the balance shifts and more goes toward paying down the principal.
On an interest-only mortgage, your monthly payment covers just the interest — the loan balance stays the same throughout. You need a separate plan to repay the capital at the end of the term, such as savings, investments, or selling the property.
A repayment mortgage guarantees the loan is paid off by the end of the term. Monthly payments are higher, but you build equity with every payment and owe nothing at the end. This is the most common type for residential buyers.
Interest-only mortgages have lower monthly payments but carry more risk. The full loan amount is still owed at the end of the term, and lenders will want to see a credible repayment strategy. They are more common with buy-to-let investors, where rental income covers the interest and the property is sold to clear the debt.
Most lenders require a minimum deposit of 5–10% of the property price, though a larger deposit typically gets you a better interest rate. At 10% deposit, you are borrowing at a 90% loan-to-value (LTV) ratio. At 25% deposit, you reach 75% LTV, which is where the most competitive rates tend to start.
The deposit also affects affordability. A larger deposit means a smaller loan, which means lower monthly payments and less total interest paid over the life of the mortgage. Even a small increase in deposit can make a noticeable difference to what you pay each month.
This calculator gives you the core monthly payment, but the true cost of a mortgage includes arrangement fees, valuation fees, legal costs, and potentially early repayment charges. Some lenders offer fee-free products at a slightly higher rate — whether that works out cheaper depends on how long you stay on the deal.
Most fixed-rate deals last two or five years. When the deal ends, you move to the lender’s standard variable rate (SVR), which is usually significantly higher. Most borrowers remortgage before that happens.
Already have a mortgage? Use our mortgage overpayment calculator to see how extra payments could shorten your term and save on interest. Buying a property? The stamp duty calculator estimates your SDLT bill. For long-term savings, try the ISA calculator to project tax-free growth.
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