Mortgage Overpayment Calculator
Should you overpay your mortgage or save the money and pay it off later?
Mortgage Details
% of balance you can overpay per year without penalty (typically 10%)
Charge applied if you exceed your overpayment allowance
Your Spare Money
Enter one or both of the amounts below. Each feeds into different scenarios — the calculator will compare them all and recommend the best option.
Lump Sum
A one-off amount you have available. Used in scenarios 1, 3, 4, and 6.
Monthly Amount
An amount you could spare each month. Used in scenarios 2, 3, 5, and 6.
Time Horizon
How long you have spare money available. For overpayment scenarios, this is how many months you make extra payments. For save-then-pay scenarios, this is how long the money sits in savings before being applied to the mortgage. Affects 5 of 6 scenarios.
Save First, Pay Later
For scenarios 4, 5, and 6: instead of paying the mortgage straight away, you put the money into a savings account to earn interest first. After the duration ends, the total pot (your money + interest earned) is applied to the mortgage as a single overpayment.
Tax Settings
Affects tax on savings interest in "save then pay" scenarios. Personal Savings Allowance applies before tax.
How It Works
This calculator compares six strategies for using your spare money, all measured against a baseline of just making your normal mortgage payments. Each scenario is calculated independently.
Overpay Now
Lump Sum Overpayment
Pay a lump sum directly off the mortgage now.
Enter a lump sum amount to enable this scenario.
Monthly Overpayment
Pay extra on top of your regular mortgage payment each month.
Enter a monthly amount and duration to enable this scenario.
Lump Sum + Monthly Overpayment
Apply both a lump sum and monthly overpayments to the mortgage at the same time.
Enter both a lump sum and a monthly amount (with duration) to enable this scenario.
Save First, Pay Later
Save Lump Sum, Then Pay
Put the lump sum into savings to earn interest, then apply the total to the mortgage later.
Enter a lump sum amount and duration to enable this scenario.
Save Monthly, Then Pay
Save monthly into a savings account, then apply the total pot to the mortgage later.
Enter a monthly amount and duration to enable this scenario.
Save Lump Sum + Monthly, Then Pay
Save both your lump sum and monthly amount into savings, then apply the combined pot to the mortgage later.
Enter both a lump sum and a monthly amount (with duration) to enable this scenario.
The baseline (normal payments, no overpayments) is always calculated. Scenarios only appear in the results when their required inputs are filled in.
Disclaimer: This calculator is for informational purposes only and does not constitute financial advice. Results are estimates based on your inputs and assume a fixed interest rate for the remainder of the term. Actual results may vary. Always check your mortgage terms and consult a financial adviser before making overpayments.