Mortgage Cost Check: A Free UK Mortgage Calculator for Clearer Planning

Property decisions come with a lot of numbers. A small change to the deposit, mortgage term or interest rate can make a noticeable difference to the monthly payment and the amount of interest paid over time.

That is why I created Mortgage Cost Check: to give people a simple place to test those variables and see an immediate, easy-to-read illustration.

Why I created Mortgage Cost Check

Mortgage calculators are useful, but the result is often presented as a single monthly figure. I wanted to make the wider cost clearer. The monthly payment matters, yet so do the amount borrowed, loan-to-value ratio, total estimated interest, potential property tax and the effect of making overpayments.

The aim is not to tell you which mortgage to choose. It is to help you arrive at a conversation with a lender, broker or financial adviser with better questions and a clearer sense of the scenarios you want to explore.

What can Mortgage Cost Check calculate?

The main calculator brings several useful estimates into one screen:

• Estimated monthly capital-and-interest repayment
• Estimated monthly interest-only payment
• Mortgage amount after your deposit
• Loan-to-value ratio, commonly shortened to LTV
• Estimated interest across the mortgage term
• Potential time and interest saved through monthly overpayments
• An indicative property-tax estimate based on the location and buyer type selected
• A downloadable PDF summary of your figures

How to use the free UK mortgage calculator

1. Enter the property price. Use the price of a home you are considering or a sensible budget figure.
2. Add your deposit. The calculator subtracts this from the property price to estimate the mortgage required.
3. Choose the mortgage term. Compare different terms to see the effect on monthly repayments and estimated total interest.
4. Enter an interest rate. Use a realistic example from your research, then test a higher rate to see how the payment could change.
5. Try an overpayment. Add a regular extra monthly amount to illustrate how it may reduce the term and interest.
6. Review and save. Compare the results and download a PDF summary if you want to keep the scenario.

Because the fields update the results quickly, you can compare several scenarios without creating separate spreadsheets.

Repayment and interest-only mortgages: what is the difference?

With a repayment mortgage, each monthly payment covers interest and repays some of the capital borrowed. If all contractual payments are made, the mortgage should be repaid by the end of its term.

With an interest-only mortgage, the monthly payment covers only the interest. The original capital remains outstanding and must be repaid at the end of the term using an acceptable repayment strategy. The Financial Conduct Authority stresses the need for interest-only borrowers to have a credible way to repay that capital.

Mortgage Cost Check shows both estimated monthly figures side by side. The lower monthly cost of an interest-only illustration should therefore never be read as the full cost of repaying the debt.

Further reading: MoneyHelper's guide to repayment options and the FCA's interest-only mortgage information.

How your deposit affects the mortgage and LTV

Loan-to-value compares the amount borrowed with the property price. For example, if the mortgage represents 80% of the property value, the LTV is 80%. Increasing the deposit reduces the amount borrowed and therefore lowers the LTV.

Seeing the mortgage balance and LTV together is helpful when you are testing deposit sizes. It makes it easier to understand the relationship between the cash you put in and the proportion of the home's value you need to borrow.

What could mortgage overpayments change?

Adding money above the normal monthly repayment can reduce the outstanding balance more quickly. That can mean less future interest and an earlier repayment date. Mortgage Cost Check illustrates both the estimated interest saving and the shortened term.

However, your mortgage agreement may limit overpayments or apply an early repayment charge. MoneyHelper recommends checking the terms of your deal before paying extra. An illustration is useful for planning, but the lender's rules determine what you can actually do.

Independent guidance: MoneyHelper — should you pay off your mortgage early?

More calculators for specific mortgage questions

The site also includes focused tools for common situations:

• Interest-only mortgage calculator: estimate the monthly interest and see the capital remaining at the end.
• Mortgage overpayment calculator: explore possible interest savings and a shorter repayment term.
• First-time buyer calculator: check the relationship between property price, deposit, LTV and an indicative property-tax figure.
• Remortgage calculator: compare an existing rate with a different example rate.
• Mortgage amortisation calculator: estimate the balance remaining at a point in the term.

What the calculator cannot tell you

A calculator is an illustration, not a personalised assessment. Mortgage Cost Check does not know your income, household spending, credit history, age, employment, other debts or a lender's individual criteria. It also assumes the example interest rate remains fixed for the full term and does not include product fees or future rate changes.

Property-tax figures can also depend on location, eligibility, ownership and transaction details. Check any estimate against the relevant official tax authority or ask a conveyancer before relying on it.

Use the results to explore and compare, then speak to a qualified mortgage professional for advice based on your circumstances.

Start with the numbers, then ask better questions

The real value of a mortgage calculator is not finding one perfect result. It is seeing how the result moves when your assumptions change. Try different deposits, terms, interest rates and overpayments. Save the most useful scenarios, then take them into your next conversation with a broker or lender.

Mortgage Cost Check is free, quick to use and designed for exactly that kind of practical exploration.

This article is for general information only and is not financial advice. Calculator results are estimates based on the information entered and assumptions explained on the site.