MathBench

Early Mortgage Payoff Calculator

Enter your loan and an extra payment, monthly, one-time, or both, and see the new payoff date, the interest saved, and both balance curves on one chart.

Educational estimates only. This calculator is for planning and education. It is not financial, tax, or investment advice, and results may differ from what a lender, broker, or the IRS calculates for your situation. Confirm important decisions with a qualified professional.

Don't know it? The mortgage calculator computes it.

Result

—new payoff time
—sooner than current path
—interest saved
—total interest (new plan)

How this calculator works

The calculator amortizes your loan twice: once on the current path, and once with your extra payments applied to principal. Each month it charges interest on the remaining balance, applies your payment, and subtracts what's left from principal, the same arithmetic your servicer runs. The difference between the two runs is the story: the new payoff date, the months eliminated, and the interest those months would have cost.

Use the monthly field for a recurring extra amount, the one-time field for a lump sum applied today, or both. Enter only the principal-and-interest part of your payment: escrow for taxes and insurance passes through to other parties and doesn't amortize anything.

The formula

Each month:
  interest  = balance × (rate ÷ 12)
  principal = payment + extra − interest
  balance   = balance − principal

repeated until balance = 0, for both scenarios.
Interest saved = Σ interest (current) − Σ interest (accelerated)

This is standard fixed-rate amortization with the final payment prorated. The lump sum, if any, is subtracted from the balance before month one. The model assumes a fixed rate and that extras post to principal. See the FAQ on making sure your servicer does that.

Worked example

Say you owe $300,000 at 6.5% with a $1,900 monthly P&I payment, and you add $200 extra each month:

  1. Current path: 358 months (29 yrs 10 mo), $379,815 total interest
  2. With $200 extra: 276 months (23 yrs), $277,817 total interest
  3. Time saved: 82 months, 6 years 10 months
  4. Interest saved: 379,815 − 277,817 = $101,998

Add a one-time $10,000 principal payment today and the loan closes in 256 months with $245,838 of interest. The lump sum alone is worth another $32,000 in interest over the life of the loan.

Assumptions & tips

  • Confirm where the extra lands. After your first extra payment, check the statement: the balance should drop by the extra amount on top of normal principal. If it shows as "paid ahead," call the servicer.
  • Keep the emergency fund first. Money paid into principal can't be taken back out without refinancing or selling, so build liquid savings before making extra payments.
  • Early dollars work hardest. The same $10,000 lump saves far more in year 2 than in year 22, because it stops interest for longer.
  • Rounding up is a painless start. Rounding a $1,896 payment to $2,000 is barely felt month to month but compounds into years off the term. Run your own numbers above.
  • High-interest debt outranks the mortgage. Extra dollars aimed at a 22% credit card "earn" more than triple what they earn against a 6.5% mortgage.

Frequently asked questions

Should extra payments go to principal or the next payment?

Principal, and it usually has to be said explicitly. Most servicers apply unmarked extra money as a prepayment of next month's bill, which saves you nothing in interest. Mark the extra amount "apply to principal" (most online portals have a field for it) and check the next statement to confirm the balance dropped by the full extra amount.

Is paying extra on the mortgage better than investing the money?

Paying principal earns you a guaranteed, tax-free return equal to your mortgage rate. A 6.5 percent loan means every extra dollar reliably "earns" 6.5 percent. Whether that beats investing the same dollars depends on market returns, your tax situation, and how much you value certainty. This calculator shows only the mortgage side of that comparison. That trade-off is a personal decision worth discussing with a financial professional.

Do extra payments lower my monthly payment?

No: on a standard fixed-rate mortgage, the required payment stays the same and the loan ends sooner. The exception is a recast: some servicers will re-amortize the loan over the remaining term after a large lump-sum principal payment (often for a small fee), which lowers the payment instead of shortening the term.

Do prepayment penalties still exist?

They are rare on standard conforming loans made after 2014, but some jumbo, investment-property, and non-qualified loans still carry them, typically limited to the first three years. One phone call to your servicer (or a look at your closing disclosure's "Prepayment Penalty" line) settles it before you send the first extra dollar.

Sources

  1. How does paying down a mortgage work? Consumer Financial Protection Bureau. consumerfinance.govThe CFPB's account of amortization (why early payments are mostly interest and later ones mostly principal), which is the month-by-month mechanic this page simulates.
  2. Regulation Z, 12 CFR §1026.36(c), Servicing practices — payment processing. Consumer Financial Protection Bureau. consumerfinance.govThe federal rules on how a servicer must credit a periodic payment and how it may hold a partial payment in a suspense or unapplied-funds account: the mechanics that make it worth checking the next statement after sending extra money.
  3. Can I be charged a penalty for paying off my mortgage early? Consumer Financial Protection Bureau. consumerfinance.govWhether a payoff or a large prepayment triggers a penalty, and where to look on your loan documents.
  4. What is a prepayment penalty? Consumer Financial Protection Bureau. consumerfinance.govBacks the FAQ's claim that penalties normally apply only to a full payoff within the first few years, not to small extra principal payments.
  5. Regulation Z, 12 CFR §1026.43(g), Prepayment penalties. Consumer Financial Protection Bureau. consumerfinance.govThe federal restrictions (covered transactions, the three-year limit and the stepped-down caps) that make prepayment penalties rare on standard loans made since the rule took effect in January 2014.

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