Mortgage Overpayment Calculator.
Use this Mortgage Overpayment Calculator to estimate how extra payments could reduce your mortgage term and lower the total interest you pay. Enter your remaining balance, APR, and term, then add a monthly overpayment and/or an annual lump sum to see the potential impact instantly.
This tool is designed for quick planning and comparison. It provides an estimate, not financial advice.
Mortgage Overpayment Calculator
See how mortgage overpayments could reduce your term and the total interest you pay. Results update instantly as you change values.
How to use the Mortgage Overpayment calculator
- Enter your mortgage balance, interest rate (APR), and remaining term.
- Add either (or both):
- an extra monthly overpayment, and/or
- an annual lump sum overpayment (choose the month it is paid).
- Optionally add a start date to estimate a payoff date.
- Results update immediately. Click Reset to start again.
What the results tell you
- Estimated monthly payment (no overpayment): The calculated payment based on your balance, APR, and term.
- New term (with overpayments): How long the mortgage could last if you keep paying the same base payment and add the overpayments.
- Time saved: The difference between the baseline term and the overpayment scenario.
- Interest saved: The difference in total interest paid between the two scenarios.
- Estimated payoff date: A simple date estimate based on the start date you enter.
Important UK notes (read this)
- Many UK lenders allow overpayments but can cap them (often around 10% per year) and may charge early repayment charges, particularly during fixed-rate periods.
- Lenders also have different rules for how they apply overpayments (for example, reducing your term vs recalculating payments).
- This calculator assumes your base payment stays the same and you add the overpayments on top.
Examples for Mortgage Overpayment Calculator Online
Example 1: £200,000 at 4.5% over 25 years
If you add £100 per month, you’ll typically see a shorter term and lower total interest than if you make no overpayments.
Example 2: Annual lump sum
If you pay a £1,000 lump sum once per year (for example, after a bonus), the balance reduces faster than the baseline scenario, which can save interest.
Example 3: Combine monthly and lump sum
Combining a small monthly overpayment with an annual lump sum often creates a bigger difference than either method alone.
FAQs for Mortgage Overpayment
How do mortgage overpayments reduce interest?
Because interest is usually calculated on the remaining balance, reducing the balance sooner can reduce the interest charged over time.
Is there a limit on overpayments in the UK?
Often yes. Many lenders cap overpayments (frequently around 10% annually) and may charge early repayment fees. Check your mortgage offer and terms.
Does this calculator match my lender’s exact figures?
Not always. It estimates payments from your inputs and models overpayments. Lender calculations can vary due to product rules, rounding, and fee structures.
What’s better: monthly overpayments or annual lump sums?
It depends on timing and cash flow. Paying earlier generally reduces interest sooner, but both approaches can be effective.
Will overpaying always shorten my term?
Usually, if you keep the same base payment and add overpayments. Some lenders may instead recalculate your payment amount; this calculator assumes term reduction.