Mortgage Calculator UK
Work out how much your monthly mortgage repayments would be on any UK property. Enter the property price, your deposit, the interest rate, and the mortgage term to see a full breakdown of your monthly payment, total amount repaid, and total interest cost.
Your Monthly Payment
£1,500.75
per month over 25 years at 4.5%
Monthly Payment
£1,500.75
Total Repaid
£450,225.00
Total Interest
£180,225.00
| Breakdown | Amount |
|---|---|
| Property Price | £300,000.00 |
| Deposit | £30,000.00 |
| Loan Amount | £270,000.00 |
| Interest Rate | 4.5% |
| Term | 25 years |
| Monthly Payment | £1,500.75 |
| Total Repaid | £450,225.00 |
| Total Interest | £180,225.00 |
| Loan to Value (LTV) | 90.0% |
How Mortgage Repayments Are Calculated
Most UK mortgages use a repayment structure where each monthly payment covers both interest and a portion of the capital. The calculation uses what is known as the annuity formula: it takes the total loan amount, divides the annual interest rate into a monthly rate, and works out a fixed payment that will clear the entire debt by the end of the term.
In the early years, a larger share of each payment goes towards interest because the outstanding balance is still high. As you gradually reduce the capital, the interest portion shrinks and more of your payment chips away at the loan itself. By the final years, almost all of each payment is capital repayment.
This calculator uses the standard annuity formula: P = L[c(1+c)^n] / [(1+c)^n - 1], where L is the loan amount, c is the monthly interest rate, and n is the total number of monthly payments. The result is a single fixed monthly figure for the entire term, assuming the interest rate remains constant.
Example Mortgage Calculations
The following examples illustrate typical repayment scenarios at different price points and deposit sizes. All assume a standard repayment mortgage with a fixed interest rate for the full term.
First-time buyer: £250,000 property, 10% deposit, 4.5% rate, 30 years
With a deposit of £25,000 on a £250,000 property, the mortgage amount is £225,000 at 90% LTV. At 4.5% over 30 years, the monthly payment would be approximately £1,140. Over the full term you would repay around £410,400, of which roughly £185,400 is interest.
Growing family: £400,000 property, 20% deposit, 4.0% rate, 25 years
An £80,000 deposit on a £400,000 home gives a £320,000 loan at 80% LTV. At 4.0% over 25 years, the monthly payment comes to roughly £1,689. The total repaid would be about £506,700, with approximately £186,700 in interest.
Downsizer: £200,000 property, 50% deposit, 3.5% rate, 15 years
A substantial £100,000 deposit halves the loan to £100,000 at 50% LTV. At 3.5% over 15 years, the monthly payment is around £715. The total cost would be roughly £128,700, with only about £28,700 in interest — far less than longer terms.
What Affects Your Mortgage Rate
The interest rate you are offered depends on several factors, and understanding them can help you secure a better deal.
Loan-to-value ratio
LTV is the single biggest factor in the rate you are offered. Lenders group their products into LTV bands — typically 60%, 75%, 80%, 85%, 90%, and 95%. Rates improve significantly as you move into a lower band. If your deposit puts you just above a threshold, it may be worth finding a little more to drop into the next tier.
Mortgage term
Shorter terms generally attract slightly lower rates because the lender's money is at risk for a shorter period. However, the monthly payments are higher. A 25-year term is the most common in the UK, though terms of 30 and even 35 years are increasingly available to keep monthly costs manageable.
Fixed vs variable rates
Fixed-rate mortgages lock in your rate for a set period — most commonly two or five years. You pay a small premium for the certainty, but your payments will not change if the Bank of England raises its base rate. Variable rates, including trackers and discounted rates, may start lower but can rise at any time. Your choice depends on your appetite for risk and how important budgeting certainty is to you.
Frequently Asked Questions
How are monthly mortgage repayments calculated?
Monthly repayments on a standard repayment mortgage are calculated using the annuity formula. This takes the loan amount, annual interest rate, and total number of monthly payments to produce a fixed monthly figure that covers both interest and capital. Each month, a slightly larger share of the payment goes towards the capital as the outstanding balance falls.
What is loan-to-value (LTV) and why does it matter?
Loan-to-value is your mortgage amount expressed as a percentage of the property price. For example, a £270,000 mortgage on a £300,000 property gives an LTV of 90%. Lenders offer better interest rates at lower LTVs because the loan is less risky. Dropping below key thresholds — such as 90%, 80%, or 75% — can unlock noticeably lower rates.
What deposit do I need to buy a house in the UK?
Most UK lenders require a minimum deposit of 5% of the property price, though some government-backed schemes may accept less. A 10% deposit opens up a wider range of products, and putting down 15% to 25% typically gives you access to the most competitive rates. The larger your deposit, the lower your LTV and the less interest you pay overall.
Should I choose a fixed or variable rate mortgage?
A fixed rate keeps your monthly payment the same for a set period, usually two or five years, giving you certainty over your budget. A variable rate can go up or down with the Bank of England base rate or your lender’s standard variable rate. Fixed rates are generally higher initially but protect you from rate rises. Variable rates may be cheaper if rates fall but carry more risk.
Can I overpay my mortgage to reduce interest?
Most UK mortgage deals allow overpayments of up to 10% of the outstanding balance per year without early repayment charges. Overpaying reduces your capital faster, which means you pay less interest over the life of the mortgage and could pay it off sooner. Always check your mortgage terms before making overpayments, as exceeding the allowance may incur penalties.
How does the mortgage term affect my payments?
A longer term spreads the loan over more months, reducing each monthly payment but increasing the total interest paid. For example, the same loan at the same rate costs less per month over 30 years than over 20 years, but you pay significantly more in total interest. Choosing the shortest term you can comfortably afford will minimise your overall cost.
Important Disclaimer
The figures provided by this calculator are estimates based on the information you enter and published rates at the time of writing. They do not constitute financial, tax, or legal advice, and we accept no liability for decisions made on the basis of these estimates. Your actual liability may differ depending on your individual circumstances, applicable reliefs, and any changes to rates or legislation. Always consult a qualified professional or check the latest HMRC guidance at gov.uk before making financial decisions.
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