UK Mortgage Calculator

Form

Home Price £

Mortgage Deposit (%)

Interest Rate

Loan Term (Years)

include option below

Annual property-related rate (%)

Annual Home Insurance £

Annual Mortgage Insurance £

Annual Other Costs £

Results

1 What is UK Mortgage?
2 How to Use This Calculator
3 Formula Used
4 Variables Explained
5 Worked Example
6 Why Use This Calculator?
7 Common Mistakes
8 Frequently Asked Questions
9 Sources & References
10 Related Calculators

What is UK Mortgage?

This UK mortgage calculator estimates a level monthly capital-and-interest repayment from home price, deposit percentage, term and a constant annual interest rate. It also shows a monthly interest-only reference. Optional annual amounts can be spread across months to form a broader budgeting figure.

It is an illustration, not a lender quotation or affordability decision. UK mortgage rates can be fixed for an initial deal then change, and fees may be added to the loan. The model holds one rate for the full term and does not include stamp taxes, product fees, valuation, legal costs or early-repayment charges.

How to Use This Calculator

Enter the home price in pounds.
Enter the deposit as a percentage of price, below 100%.
Enter the annual mortgage rate and whole-year term.
Optionally include an annual property-related rate and annual insurance or other costs.
Select Calculate and review the repayment, interest-only reference, borrowing amount and total interest.

The optional property percentage is a generic estimate based on price. UK Council Tax is normally band- and authority-based rather than a percentage of property value, so do not use that field as an official Council Tax calculation. Optional annual costs are assumed constant across the entire term.

Formula Used

Deposit amount = home price × deposit percentage; loan = price − deposit. With monthly rate r and n payments, monthly repayment = Lr(1+r)ⁿ ÷ ((1+r)ⁿ−1). At zero interest it is L ÷ n. The interest-only reference is Lr.

Total modeled mortgage payments equal monthly repayment × n, and total interest equals that total minus L. Optional annual amounts are divided by 12; the property-related percentage is price × percentage ÷ 12.

Variables Explained

Input or result	Meaning
Home price	Purchase price in pounds.
Deposit	Percentage paid upfront under this model.
Loan amount	Price minus modeled deposit.
Interest rate	Nominal annual rate assumed constant and divided by 12.
Repayment	Level monthly capital-and-interest amount.
Interest-only	Monthly interest reference that does not repay principal.

Worked Example

For a £250,000 home, 25% deposit, 5% annual rate and 25-year term, the deposit is £62,500 and loan is £187,500. The monthly rate is 0.05 ÷ 12 and there are 300 payments.

The repayment formula gives £1,096.11 per month. The initial interest-only reference is £187,500 × 0.05 ÷ 12 = £781.25. Modeled repayment total is £328,831.90 and total interest is £141,331.90, subject to endpoint rounding and the constant-rate assumptions.

Why Use This Calculator?

A repayment mortgage payment contains interest and principal and is designed to clear the modeled balance by the end of the term. The interest-only figure covers interest at the entered rate but leaves the original principal to be repaid through a credible separate plan. MoneyHelper notes that most mortgages offered are repayment mortgages and that interest-only borrowing needs a repayment strategy.

A lower monthly payment from a longer term often means more total interest. A bigger deposit reduces the loan and may affect available rates, but this page does not predict lender loan-to-value bands. Stress-test a higher rate, particularly after an introductory deal. Compare the annual percentage rate of charge, fees, portability, overpayment terms and reversion rate, and seek regulated advice when needed.

The payment is an annuity calculation. Early payments contain more interest because the outstanding balance is larger; later payments contain more principal, even though the total repayment stays level in this simplified model. The separate interest-only amount is based on the original loan and is shown for comparison, not added to the repayment figure.

Optional totals multiply current annual costs across every year without inflation, cancellation or coverage changes. That can be useful for a consistent scenario but is unlikely to forecast decades precisely. Use present-day budgeting inputs and update them when comparing options. Buildings insurance may be required by a lender, while life or payment-protection products are separate choices.

Common Mistakes

Entering a cash deposit instead of a percentage.
Assuming the rate stays fixed for the full term.
Treating the interest-only reference as a repayment schedule.
Using the property percentage as official Council Tax.
Ignoring fees added to the balance.
Assuming optional costs remain constant for decades.
Treating the estimate as lender approval.

Frequently Asked Questions

Is the deposit entered in pounds?

No. Enter it as a percentage of the home price.

Does the monthly repayment include changing rates?

No. One annual rate is assumed for the entire term.

What does interest-only mean here?

It is one month’s interest at the entered rate and does not reduce principal.

Does the estimate include stamp duty?

No. Transaction taxes and purchase fees are outside the calculation.

Is the property-related percentage Council Tax?

No. It is only a generic price-based budgeting input.

Why can a longer term cost more overall?

More monthly periods allow interest to accrue even if each payment is lower.

Can this tell me whether a lender will approve me?

No. Affordability, credit, property and lender criteria require a formal assessment.

Sources & References

MiniCalculators provides free tools for mathematics, finance, health, fitness, construction, statistics, conversions, and everyday questions. Each calculator includes a guide to its inputs, method, and limitations.