Stable Numbers
Mortgage Overpayment Calculator
See how extra monthly payments, a lump sum, or an annual overpayment can shorten your mortgage and cut interest. Share your setup and download the schedule.
Nominal APR with monthly compounding.
You can mix years and months.
Used to label the schedule months.
Overpayments
Added on top of the standard repayment each month.
1 means the first month.
1 to 12. Applied once per year.
Baseline uses the standard annuity repayment. Overpayments reduce the balance faster which shortens the term. Final payment adjusts so you do not overpay.
Show amortisation schedule
| # | Date | Payment | Interest | Principal | Overpay | Balance |
|---|---|---|---|---|---|---|
Final payment is trimmed to clear the remaining balance. Minor rounding differences can occur.
About this calculator
The baseline monthly repayment uses the standard annuity formula based on your APR and term, with interest calculated monthly on the remaining balance. Overpayments reduce the principal faster which cuts future interest and shortens the term. You can model three types of overpayment: a fixed amount every month, a one-off lump sum in a chosen month, and a recurring annual overpayment in a chosen month of the year.
If the APR is zero the repayment is simply the balance divided by the number of months and all overpayments go straight to principal. The last month is adjusted so you do not overpay. Treat the results as a planning guide. Lenders may round at different steps which can move pence.
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