Mortgage Calculator — Monthly Payments & Total Cost

Property Value

Deposit

Annual Interest Rate

Mortgage Term

yrs

Monthly Payment

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per month

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Loan Amount

—

Total Interest

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Total Amount Repaid

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Loan to Value (LTV)

About the Mortgage Calculator

A mortgage is a loan secured against a property. Most residential mortgages in the UK are repayment mortgages, where each monthly payment reduces both the interest and the outstanding loan balance. The standard term is 25 years, though 30 and 35-year terms are increasingly common.

Factors affecting your mortgage payment

Loan amount: The property value minus your deposit
Interest rate: Fixed or variable — use your current deal rate or the lender's SVR
Term: Longer terms mean lower monthly payments but significantly more total interest
Loan to Value (LTV): Lower LTV = better rates and less risk to the lender

This calculator is for illustrative purposes. Always consult a qualified mortgage advisor before making financial decisions.

Understanding your amortisation schedule

In the early years of a mortgage, most of your monthly payment goes to interest rather than reducing the principal. On a typical 25-year mortgage, you may pay more in interest during the first 5 years than you repay in principal. This is why overpaying early in the mortgage term saves disproportionately more interest than overpaying later.

Interest front-loading — early payments are mostly interest; principal reduction accelerates over time
LTV (Loan-to-Value) — as you repay principal, your LTV improves, potentially unlocking better remortgage rates
Overpayments — most UK lenders allow 10% of balance per year without early repayment charges
Remortgaging — switching to a better rate every 2-5 years can save significant money compared to reverting to the Standard Variable Rate

Frequently Asked Questions

How is a mortgage payment calculated?

Monthly payment = P × [r(1+r)^n] / [(1+r)^n - 1], where P is the loan amount, r is the monthly interest rate (annual rate ÷ 12), and n is the total number of payments.

What is amortisation?

Amortisation is the process of paying off your mortgage over time through regular payments. Early payments are mostly interest; later payments are mostly principal.

How much deposit do I need?

In the UK, the minimum deposit is typically 5% of the property value. A 10% deposit unlocks better rates, and 20–25% typically gives access to the best mortgage deals.

What is the difference between repayment and interest-only mortgages?

With a repayment mortgage, each payment covers both interest and reduces your loan balance. With interest-only, you only pay the interest — the full loan must be repaid at the end of the term.

How does the mortgage stress test work?

UK mortgage lenders must assess whether you could afford repayments if interest rates rose by 3 percentage points above the reversion rate (typically the Standard Variable Rate). This stress test is required by the FCA. If the stressed monthly payment exceeds 40-45% of your net monthly income, the lender may decline or reduce the loan.

When should I remortgage?

Remortgage when your current fixed-rate deal is about to end (usually 3-6 months before). Staying on the Standard Variable Rate after a deal expires typically costs 1-2% more in interest. Also consider remortgaging if your LTV has improved significantly (crossed a 5% threshold like 85%, 80%, 75%) as lower LTV unlocks better rates.