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Tool

Mortgage overpayment calculator

See how much time and interest you could save by overpaying your mortgage each month.

Paying a little extra towards your mortgage each month, or a lump sum now and then, reduces the balance faster. Because interest is charged on what you still owe, that can save a surprising amount.

Enter your balance, rate and term, then add a monthly overpayment or a lump sum to see how much sooner you'd be mortgage-free and how much interest you'd avoid.

Interest you'd save

£38,458

Mortgage-free after19 years 11 months
Time saved5 years 1 month
Normal monthly payment£1,390
With your overpayment£1,590
Total interest, no overpayment£166,874
Total interest, with overpayment£128,416

Assumes the same rate for the whole term. Most deals limit overpayments, often to 10% of the balance a year, before an early repayment charge applies. Check yours first.

How this calculator works

  1. The calculator first works out your normal payment and the interest you'd pay if you only ever paid that.
  2. Then it replays the loan month by month with your extra money added, and compares the two.
  3. The difference is the time and interest you'd save.

What it assumes

  • A fixed rate for the whole remaining term.
  • Overpayments reduce the balance straight away, as most lenders do, but check how yours are applied.
  • Many deals limit overpayments, often to 10% of the balance a year, before an early repayment charge applies.

General information, not financial advice. Speak to a mortgage adviser about your own situation.

Mortgage overpayment calculator: common questions

Short answers to the things people ask most.

Is it better to overpay or save?

It depends on your mortgage rate and what your savings earn. Overpaying earns you the equivalent of your mortgage rate, risk-free, but the money is then tied up in the house. Keep an emergency fund first.

Will I be charged for overpaying?

Possibly. Many fixed-rate deals let you overpay up to a set limit each year without charge, and charge an early repayment fee on anything above it. Check your offer or ask your lender.

Should I shorten the term or lower the payment?

Most lenders reduce your term when you overpay, so you keep the same payment. Some will lower your payment instead if you ask. The term route usually saves more interest.

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