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Offset Mortgage calculator

Existing Offset Mortgage customers only

With an Offset Mortgage we take your savings into account when working out your interest. Say you have a mortgage of £100k and £20k in savings. You only pay interest on the difference – which in this case is £80k. Enter your details below to see how much your Offset Mortgage could save you in interest payments.

Your mortgage details

Your mortgage details

What could you save by Offsetting

What could you save by Offsetting

could save you
per month
which is
over the term of your mortgage.

The benefits of Offsetting


Offsetting monthly payment
Offsetting total interest payable

Without Offsetting

Without Offsetting monthly payment
Without Offsetting total interest payable

How we calculate these savings

  • the calculator assumes your interest rate will stay the same for the term of your mortgage
  • we’ve evened out the months so they’re all the same length – 30.4 days each – so monthly interest will be consistent
  • repayments are rounded up or down to the nearest pound
  • we’ve rounded time saved down to the closest month
  • interest is calculated daily and added monthly
  • interest saved is rounded up or down to the nearest pound
  • the calculator assumes the total savings balance is held in a linked account(s) and remains constant throughout the term of the mortgage
  • if your total savings increase or decrease on an adhoc basis, your monthly interest payments will also change respectively.

Please note – the information in this calculator is for illustrative purposes only and isn’t a precise calculation. This information doesn’t include all of the details you need to either make an overpayment or choose a mortgage. Make sure you read the separate Mortgage Illustration before you choose a mortgage.

Find the mortgage for you

Remember: Offset Mortgages are only available to existing Offset Mortgage customers

Contact us today

If you want to: Find out more information about your existing mortgage rate

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If you want to: Move house, remortgage, discuss rates or borrow more

New to first direct

0800 48 24 48

Mon to Sat 8am - 8pm and Sun 9am - 8pm

Existing first direct customers:

03 456 100 103

Mon to Sat 8am - 8pm and Sun 9am - 8pm

If you have: Completion questions, payment changes, statement requests, or to pay off your mortgage

03 456 100 198

Mon to Fri 8am - 9pm and Sat 8am - 5.30pm

If you have: An ongoing mortgage application

03 456 100 173

Mon to Sat 8am - 8pm and Sun 9am to 8pm