Mortgage Calculator

Learn how to use a mortgage calculator to estimate and compare your mortgage costs and options. Find out what inputs you need and what outputs you get.

This only affects the "Where you stand today" part of the results
If you are comparing mortgages it may be useful to label your results

Note: The figures generated by this mortgage calculator are for illustrative purposes only and should not be considered as formal financial advice. The results are based on the information you provide and various other estimations, and they are not a guarantee or quotation from any mortgage lender. Always consult with a qualified mortgage advisor or financial professional before making any decisions based on the calculator's results.

How to use this calculator

To compare mortgages:

  1. Enter the mortgage details in the form and click 'calculate',
  2. Amend the input values and click 'calculate' again to compare 2 or more mortgages side by side.

What does the calculator do?

If you are thinking about remortgaging or comparing mortgages, use our mortgage calculator to quickly:

  • Calculate monthly repayments
  • Check how much you can afford
  • Calculate the total lifetime cost of the mortgage
  • See the impact of interest rate changes
  • See the benefits of making overpayments

If you are comparing an existing mortgage, the calculator will also show you

  • Your current outstanding balance
  • How much of your loan you have repaid to date
  • How much interest you have paid

What is a mortgage?

A mortgage is a loan from a bank or building society that helps or enables someone to buy a property.

There are two basic types of mortgage;

  • Repayment mortgage where in addition to paying the interest on the loan, a small part of the loan itself is repaid each month.
  • Interest only mortgage where only the interest is paid and the amount initially borrowed is then settled in full at the end of the mortgage.

Why is it so difficult to compare mortgages?

Comparing the real costs of different mortgages can be more complicated than it first appears. The variety of factors affecting the overall cost of different mortgage products includes interest rates, fees, term lengths, discount periods and penalties.

Additionally, some mortgages may allow for overpayments or payment holidays, which can alter the long-term financial implications. Understanding the true cost of a mortgage requires detailed analysis beyond just comparing initial interest rates or monthly payments, making it essential to look at the total cost over the life of the loan in the context of your financial situation and future plans.

Advanced mortgage calculator

Welcome to our advanced mortgage calculator, designed to simplify the financial aspects of remortgaging and comparing mortgages. Whether you're planning to switch lenders, assess new mortgage deals, or simply understand your current mortgage position better, our tool will calculate and compare:

  • Monthly repayments
  • Affordability
  • Total mortgage cost: Look at the total cost over the life of the mortgage
  • Interest rate impact
  • Overpayment benefits

If you want to analyse your existing mortgage, our calculator can also calculate your:

  • Outstanding balance
  • Amount repaid
  • Interest paid to date.

How much can I afford to borrow?

Lenders will determine how much you can afford to borrow by assessing your income, credit history, existing debts, and monthly expenses. They will then calculate the debt-to-income (DTI) ratio, calculated ad follows:

(Total monthly debt payments / Total gross monthly income) x 100 (expressed as a percentage)

Lenders will also consider your employment stability, savings, and the loan-to-value (LTV) of the property.

Do mortgage lenders have specific lending criteria?

Lending criteria vary significantly between mortgage lenders, influenced by their risk appetite, target market (e.g. buy to let mortgages or auction mortgages), and regulatory compliance. These differences can affect loan-to-value (LTV), income and employment requirements, credit history, the types of property they will lend on and many other factors.

You can check your lender’s specific requirements at UK Finance Mortgage Lenders Handbook .

Mortgage terms and definitions

The following is a guide to mortgage terms and definitions used in the calculator results and more generally when applying for a mortgage:

Agreement In principle (AIP)

A preliminary approval from a mortgage lender estimating how much you can borrow, based on your financial information.

Annual percentage rate of charge (APRC)

The total cost of the mortgage per year, including interest and fees, expressed as a percentage.

Arrangement fees

Charges levied by lenders for setting up the mortgage.

Base rate

The interest rate set by the Bank of England (BoE) influences lenders' interest rates.

Capital repayment

A payment made towards the amount borrowed, reducing the mortgage balance.

Decision in principle (DIP)

The same as an AIP, this is a lender's indication that they may lend a certain amount based on initial financial assessment of the borrower/s.


The upfront cash payment made by the buyer towards the property's total purchase price.

Discount mortgage

A type of mortgage that offers a reduction on the lender’s standard variable rate (SVR) for a set period (typically 2 to 5 years).

Discounted rate

The interest rate applied after a discount is applied to the SVR.

Early repayment charge

A fee charged by lenders if the mortgage is repaid early or overpaid beyond agreed limits.

Exit fee

A charge levied by the lender for processing the mortgage account closure.

Fixed rate mortgage

A mortgage with an interest rate that remains the same for a specified period.

Flexible mortgage

A type of mortgage that allows greater flexibility in repayment terms, such as overpayments, underpayments, and payment holidays.

Interest rate

The percentage charged on the borrowed mortgage amount.

Loan to value (LTV)

The ratio of the loan amount to the value of the property, expressed as a percentage.

Monthly repayments

Regular payments made to cover the mortgage interest and reduce the capital.

Mortgage agreement start date

The date when the mortgage agreement officially begins.

Mortgage term

The duration over which the mortgage is to be repaid (typically 25 years).


The lender or financial institution that provides the mortgage.


The borrower who takes out the mortgage to buy the property.

Negative equity

Occurs when the value of the property falls below the outstanding balance on the mortgage.

Offset mortgage

A mortgage where savings are offset against the mortgage balance, reducing the interest paid.

Outstanding balance

The remaining amount owed on the mortgage.


Paying more than the regular monthly mortgage repayment, thus reducing the balance faster.

Payment holiday

An agreed period during which you are not required to make mortgage payments.

Product period

The duration of a specific mortgage rate or deal.

Self certification mortgage

A type of mortgage where the borrower self-declares their income, less common now due to regulatory changes.

Standard variable rate (SVR)

The default interest rate lenders charge after an initial discount period ends.

Total repayment over loan

The total amount paid back over the life of the mortgage, including interest and capital.

Tracker mortgage

A type of mortgage with an interest rate that increases or decreases in line with the Bank of England’s base rate.

Total annual payment

The amount of money paid annually that directly reduces the outstanding balance of a mortgage, excluding interest


Paying less than the regular monthly mortgage amount, subject to lender's agreement.


Mortgage calculators are useful tools to help you plan your finances and make informed decisions about your mortgage. However, they are only indicative and do not guarantee that you will get the exact amount, rate, or terms indicated. You should always get a quote from a lender and check the details carefully before applying for a mortgage. You may want to speak to a financial advisor before taking out a mortgage.

Article by Completely Moved authors

The Completely Moved team have years of experience helping home buyers, sellers and owners, answering questions and providing property advice.

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