Mortgage Extra Payment Planner
Model recurring, annual and one-off principal reductions with a full allocation ledger.
Your inputs
Use consistent units and periods. Defaults are examples.
Your result
Check the assumptions below before relying on a result.
Formula and method
Each month accrues interest at annual rate/12. Apply the original scheduled payment, then eligible monthly extra, annual extra at months 12/24/etc., and any listed lump sums. Cap the final cash payment to principal plus interest. Compare payoff time and total interest against the same loan without extras.
Worked example
At zero interest, a 1,000 balance over ten months requires 100 per month. Adding 25 extra every month clears it in eight months. Total cash paid is still 1,000; the benefit is a shorter term, not interest savings at a zero rate.
Related calculations
Mortgage Recast Calculator
Compare a lower recast payment with keeping the old payment after the same principal reduction.
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Compare actual payment dates, annual cash budgets and accrued payoff balances under one daily-interest convention.
Open calculator ↗How to use this result
- Enter the remaining balance, rate and term.
- Choose monthly extra and its start/end months.
- Add annual extra and specific month-indexed reductions if needed.
- Review the final capped payment and compare the original schedule with the accelerated schedule.
Questions about this calculation
Does extra principal reduce the required monthly payment?
The planner keeps the original scheduled payment. It reduces the payoff time; use the recast tool for a lower required payment.
Will later planned extras still be charged after payoff?
No. The calculation stops when the debt is cleared.
How are two lump sums in the same month handled?
Their amounts are added, then capped at the remaining principal after the regular payment.