Lump Sum Mortgage Repayment Calculator
See how a one-off lump sum payment towards your mortgage reduces total interest and shortens your remaining loan term.
Your results
Calculation breakdown
- New balance
- Current balance − lump sum
- Re-amortise
- Keep the same repayment, recalculate months to clear the new balance
Worked example
Putting a $30,000 lump sum into a $500,000 loan at 6% over 25 years can save around $60,000 in interest and finish the loan roughly 2.5 years early.
Assumptions
- Assumes the existing repayment amount is kept the same after the lump sum.
- Fixed rate loans may apply break costs or limits on extra lump sum payments.
How this calculator works
This calculator applies a one-off lump sum to your current mortgage balance and re-amortises the remaining repayments, showing the interest saved and months cut from your loan compared with continuing on the original schedule.
Frequently asked questions
When is the best time to make a lump sum payment?
The earlier in the loan term a lump sum is applied, the more interest it saves, because interest is calculated on the outstanding balance each period.
Will my repayment amount change after a lump sum?
This calculator assumes you keep your existing repayment amount so the loan finishes sooner; some lenders instead let you reduce the repayment and keep the same term, which saves less interest.
Are there fees for making extra lump sum payments?
Fixed rate loans often cap extra repayments or charge break costs; check your loan terms before making a large lump sum payment.
Results are estimates only and are not financial, tax, legal or credit advice.