Extra Principal Payment Savings Calculator
See exactly how much interest you save and how many years you cut off your mortgage by paying extra principal each month, year, or as a one-time lump sum. Compare 3 strategies side by side.
| Scenario | Months | Total Interest | Total Cost |
|---|---|---|---|
| Standard Schedule | — | — | — |
| With Extra Payments | — | — | — |
How Extra Principal Payments Save Interest
Every extra dollar of principal you pay reduces the balance the lender charges interest on for every remaining month of the loan. The compounding effect is enormous: an extra $200 per month on a $320,000 loan at 6.5% can save over $90,000 in interest and cut about 6 years off a 30-year term. The earlier in the loan you start, the more dramatic the savings, because interest charges are highest in the early years.
This calculator compares your standard amortization schedule against an accelerated schedule with extra payments. You can model three strategies: extra monthly, extra annual (great for tax refunds or year-end bonuses), or a one-time lump sum. The CFPB and HUD both list extra principal payments as one of the most effective ways to reduce mortgage cost (source: consumerfinance.gov).
When Extra Payments Make Sense
Extra principal payments are most powerful when your mortgage rate exceeds the after-tax return on alternative uses of the money. With 30-year fixed rates near 6.5-7% in 2026 (source: Freddie Mac PMMS), paying down a mortgage is a guaranteed risk-free 6.5% return — better than most CDs and bonds, though potentially less than long-term stock returns.
Pay extra after you have: (1) maxed out employer 401(k) match, (2) built a 3-6 month emergency fund, (3) eliminated high-interest debt above 8%. Past those priorities, extra mortgage principal beats most alternatives. Compare with our debt snowball calculator if you have multiple debts.
Make Sure Extra Goes to Principal
Always specify extra payments are for principal only — never for the next month's payment. Some lenders auto-apply extra cash to interest or future scheduled payments by default, which loses the compounding benefit. Write "principal only" on the check or use the principal-only field in your online portal. Verify on your next statement that the principal balance dropped by the extra amount.
For an alternative acceleration strategy without restructuring, see our biweekly mortgage payoff calculator (effectively 13 monthly payments per year). For a recast option after a lump-sum payment, see mortgage recast calculator.
Tax Implications
Extra principal payments do not generate any new tax deduction — only mortgage interest is deductible (and only if you itemize). However, they do reduce future deductible interest, so if you are a high earner using the mortgage interest deduction, factor that into the decision. Most filers use the standard deduction in 2026 ($15,000 single, $30,000 married filing jointly per IRS bracket adjustments) and gain no tax benefit from interest, making extra principal payments a clear win.
Last updated April 2026. Sources: cfpb.gov, freddiemac.com, irs.gov Pub 936.