Scheduled
Original path
Mortgage Overpayment Calculator
Estimate how an extra monthly mortgage payment could change payoff time and financing cost on a remaining balance.
Overpayment payoff comparison
Measure the term removed and financing cost avoided before committing liquid cash to principal.
Enter your figures, then press “Compare the overpayment path” to calculate your result.
No result yetComplete the fields and use the calculation button.
How recurring overpayments affect a mortgage
The calculator derives the scheduled payment from the remaining balance, rate and term, then runs a second schedule with the extra amount applied every month. It compares payoff time and financing cost.
- The model assumes a constant rate and monthly payment.
- Check prepayment rules and lock-in terms first.
- Overpaid cash becomes less liquid.
Verify how the facility treats extra cash
Some facilities reduce principal immediately, while others hold advance payments or apply conditions during a lock-in period. Confirm the treatment, notice requirements and charges in the current contract.
An offset or flexible facility may preserve access differently from an irreversible principal payment. The calculator does not value that flexibility.
Protect liquidity before shortening the term
Home equity is not the same as cash available for an urgent bill. Keep a suitable reserve and near-term sinking funds before directing all monthly margin to the mortgage.
Compare the avoided financing cost with other expensive debt, employer benefits and required insurance. The mathematically fastest payoff is not always the strongest full-household sequence.
Overpayment shortens a contract but locks up cash
Check facility rules and household liquidity before treating the modeled saving as available.
Extra
Principal overage
Finish
Shorter model
Keep the overpayment rule simple
A fixed recurring amount is easy to audit. Review the statement to confirm principal fell as expected and that the scheduled instalment did not silently change.
If income varies, use a smaller base overpayment and a written strong-month rule. Recalculate after rate changes because both the normal schedule and the value of overpayment will change.
- Scheduled payment
- Payment with overage
- Months removed
- Modeled financing cost avoided
Common questions about this calculator
Can an overpayment be withdrawn later?
That depends on the financing product. Ordinary principal reduction may be irreversible, while flexible or offset features can have different access rules.
Does the calculation allow for rate changes?
No. It holds the entered rate constant. Recalculate when a floating rate changes because both the normal schedule and overpayment benefit will move.