Everyday tool · ≈ 2 min · Home & mortgage
Extra Mortgage Payment Calculator
See exactly what adding a little to each mortgage payment does to your payoff date and lifetime interest.
Showing example defaults — change any input to use your own
Extra-payment impact
Estimated interest saved
$75,157
$250/month extra retires the loan in 18 yr 11 mo instead of 24 yr 4 mo — 5 yr 5 mo sooner. Each prepaid dollar stops accruing interest at 6.5%.
- Payoff, current schedule
- 24 yr 4 mo
- Payoff, with extras
- 18 yr 11 mo
- Time saved
- 5 yr 5 mo
- Interest, current schedule
- $297,124
- Interest, with extras
- $221,967
Balance over time: current vs. with extras
View data table
| Current schedule | With extras | |
|---|---|---|
| Yr 0 | $300K | $300K |
| Yr 2 | $289K | $283K |
| Yr 4 | $277K | $263K |
| Yr 6 | $263K | $241K |
| Yr 8 | $247K | $215K |
| Yr 10 | $228K | $186K |
| Yr 12 | $208K | $153K |
| Yr 14 | $184K | $116K |
| Yr 16 | $157K | $73K |
| Yr 18 | $126K | $24K |
| Yr 20 | $92K | — |
| Yr 22 | $52K | — |
| Yr 24 | $6.6K | — |
| Yr 25 | $0 | — |
What this may mean for you
Before committing extras here, the usual order of operations: high-interest debt first, then an emergency cushion, then this-versus-investing as a judgment call — prepayment's 6.5% is guaranteed, investment returns aren't. Tell your servicer extras are for principal, and keep the habit boring and automatic.
Results are estimates for educational purposes and may not reflect your complete financial or tax situation.
Understanding this calculator
Extra principal payments are the rare financial move with a guaranteed, knowable return: every dollar of principal you prepay stops accruing interest at your mortgage rate, tax-free, for the rest of the loan. At 6–7% rates the effect is dramatic — modest monthly extras routinely erase years of payments.
The comparison worth running before you commit: could those dollars do more elsewhere? High-interest debt always wins; an unfunded emergency cushion usually wins; and investing is a judgment call about return versus certainty. This calculator gives you the mortgage side of that ledger precisely.
Assumptions and methodology
- Simulates your balance monthly at the current rate and payment; extra amounts apply directly to principal.
- One-time payments apply immediately; interest saved is the difference in lifetime interest between the two schedules.
- Assumes a fixed rate and no recast; the required monthly payment stays the same until payoff.
Official sources
Last reviewed August 30, 2026. Year-specific figures show their tax or data year in the tool; data is reviewed when the IRS, SSA, and CMS publish annual updates.
Common questions
Is there a best time of month to send extras?
Sooner is mathematically better since interest accrues on the balance, but the difference within a month is small. Consistency matters far more than timing.
Should I tell my servicer anything?
Yes — mark extras as 'apply to principal.' Some servicers otherwise hold them toward the next payment, which earns you nothing.
Next step
See how this fits your whole retirement
One number is a start. The plan builder puts income, spending, savings, and taxes together year by year — free, no account, and every answer can be changed later.
Keep going
- Mortgage PayoffSee how extra monthly or one-time payments shorten your mortgage and cut total interest.Calculator
- Mortgage PaymentEstimate your full monthly payment — principal, interest, taxes, insurance, HOA, and PMI — plus total interest over the loan.Calculator
- Savings GoalTurn a savings target into either a monthly amount or a realistic finish date — with interest doing its share.Calculator
Want a professional's take? Downshift can introduce you to a financial advisor, CPA, or retirement planner who can talk through what these numbers mean for you — free to you, no obligation.
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