🏠 Mortgage Overpayment Calculator

Pay a little extra and clear your mortgage years sooner.

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Fill in the details and click Calculate to see your results.

Formula at a glance

Mortgage Overpayment Calculator: Each month — balance × (1 + r) − (payment + overpayment). Example: £250,000 at 5%, £200 a month extra → Interest saved: £44,432
How the Mortgage Overpayment Calculator works: Each month — balance × (1 + r) − (payment + overpayment)

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📘 About the Mortgage Overpayment Calculator

Every extra payment goes straight off the balance, so you pay less interest for the rest of the term. Even £100–£200 a month can cut years off a 25-year mortgage.

Fixed-rate deals often allow 10% a year without an early repayment charge. Compare the saving with what the money would earn in savings after tax, and keep an emergency fund.

🧮 Formula

Each month
balance × (1 + r) − (payment + overpayment)

✏️ Worked examples

£250,000 at 5%, £200 a month extra

You enter
Mortgage balance250000
Interest rate5%
Years remaining25 years
Extra each month200
One-off lump sum now0
Penalty-free allowance a year10%
Early repayment charge above it0%
Currency£ Pound
You get
Interest saved£44,432
Mortgage paid off5.2 years sooner (238 months left)
Normal monthly payment£1,461.48
Interest without overpaying£188,443
Interest with overpaying£144,011

£44,432 saved.

$300,000 at 6.5%, $20,000 lump sum

You enter
Mortgage balance300000
Interest rate6.5%
Years remaining28 years
Extra each month0
One-off lump sum now20000
Penalty-free allowance a year10%
Early repayment charge above it0%
Currency$ Dollar
You get
Interest saved$85,903
Mortgage paid off4.5 years sooner (282 months left)
Normal monthly payment$1,941.05
Interest without overpaying$352,192
Interest with overpaying$266,289

$85,903 saved.

🧭 How to use this calculator

What you enter

  • Mortgage balance
  • Interest rate (%)
  • Years remaining (years)
  • Extra each month
  • One-off lump sum now
  • Penalty-free allowance a year (%)
  • Early repayment charge above it (%)
  • Currency

What you get

  • Interest saved
  • Mortgage paid off
  • Normal monthly payment
  • Interest without overpaying
  • Interest with overpaying

❓ Frequently asked questions

Is it worth overpaying my mortgage?

Usually if your mortgage rate is higher than what your savings earn after tax and you have an emergency fund.

Should I reduce the term or the payment?

Reducing the term saves more interest; reducing the payment improves monthly cash flow.

How much can I overpay without a penalty?

Commonly 10% of the balance a year on UK fixed deals; check your mortgage offer.

Overpay or invest?

Overpaying is a guaranteed return at your mortgage rate; investing may earn more over long periods but with risk.