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Mortgage Payoff Calculator (Extra Payments)

See how much sooner you can pay off your mortgage and how much interest you can save by adding extra principal each month, a one-time lump sum, or switching to biweekly payments.

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Find out how much faster you can pay off your mortgage - and how much interest you can save - by sending extra principal each month, dropping a one-time lump sum, or switching to biweekly payments. Side-by-side comparison vs. the baseline schedule.

Enter your current loan balance, original APR, original term, and how many monthly payments you have already made - the calculator derives the regular monthly P&I and remaining term, then runs two amortization simulations: a baseline schedule with no extras, and an accelerated schedule with your extra monthly principal, optional one-time lump sum, and optional biweekly cadence. Worked example: $320,000 balance, 7% APR, 26 years remaining on a 30-year loan, adding $200 extra per month pays the loan off roughly 5.4 years early and saves about $83,000 in total interest. The biweekly trick (26 half-payments per year = 13 monthly payments) typically shaves 5-6 years off a 30-year loan with no other changes - you can replicate it for free by paying 1/12 extra each month or one extra payment per year.

Disclaimer: Estimates only. Confirm with your loan servicer that any extra payments are being applied to principal - some lenders default to applying unscheduled payments toward pre-paid interest or hold them until the next due date unless you explicitly mark the payment 'apply to principal.' If you itemize and deduct mortgage interest on Schedule A, your effective after-tax interest cost is lower than your APR, which reduces (but does not eliminate) the dollar benefit of prepayment shown here.

Mortgage Payoff Calculator (Extra Payments)

See how much sooner you can pay off your mortgage - and how much interest you can save - by adding extra principal each month, a one-time lump sum, or switching to biweekly payments.

Current Loan Balance ($)

Original APR (%)

Original Loan Term (years)

Payments Already Made (months)Used to derive your original loan amount and remaining term.

Extra Principal per Month ($)Any additional amount applied to principal each month.

One-Time Lump Sum ($)Optional. Applied at month 1 of the accelerated scenario.

Use biweekly payments (26 half-payments / year)Pays half the regular monthly payment every 14 days = 13 monthly payments per year.

Pay off

5 yr months early
and save $84,975 in interest

New Payoff DateJun 2047

Monthly Payment (P&I)$2,229.88

	Baseline (no extras)	Accelerated
Months to Payoff	26 yr	21 yr
Total Remaining Interest	$375,723	$290,748
Total Remaining Paid	$695,723	$610,748

Note: if you itemize and deduct mortgage interest on Schedule A, your effective after-tax interest rate is lower than your APR. The interest savings shown here are pre-tax - itemizers will keep somewhat less of the benefit because they would have deducted some of that interest.

How Extra Mortgage Payments Work

In the early years of a mortgage, the bulk of each payment goes to interest, not principal. On a $320,000 balance at 7% APR, the very first month's interest is about $1,867 - on a $2,129 P&I payment, only $262 reduces principal. Every extra dollar you send straight to principal skips all the future interest that dollar would have generated, which is why even $100-$200 extra per month can cut years off the loan and save tens of thousands in interest.

The biweekly trick: instead of one full payment each month, pay half the monthly payment every 14 days. There are 52 weeks per year, so 26 half-payments = 13 full monthly payments per year - one extra payment baked in. On a 30-year mortgage, biweekly typically shaves ~5-6 years off the loan with no other changes. Many servicers charge a fee to set this up officially; you can replicate it for free by simply paying 1/12 extra each month, or making one full extra payment annually.

Should you prepay or invest the difference? At a 7% mortgage rate, prepaying gives you a guaranteed 7% after-tax return (or close to it - your effective rate is lower if you itemize and deduct mortgage interest). The S&P 500 has historically returned ~10% annualized, so investing the difference in a low-cost index fund typically wins over 20-30 years. But mortgage prepayment is risk-free, behaviorally easy, and reduces sequence-of-returns risk - especially valuable for people near retirement who want to enter retirement debt-free. Many advisors split the difference: invest in tax-advantaged accounts first, then prepay.

Estimates assume your extra payments are applied to principal immediately. Confirm with your loan servicer - some lenders apply unscheduled payments to pre-paid interest or hold them until the next due date unless you explicitly mark the payment "apply to principal."

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Frequently Asked Questions

How much can extra mortgage payments really save?

A lot, especially early in the loan when most of each payment is interest. Example: $320,000 balance at 7% APR with 26 years remaining. Adding just $200/month extra to principal pays the loan off about 5.4 years early and saves roughly $83,000 in total interest. Going to $500/month extra cuts another 4-5 years and another $40,000+ in interest. The earlier in the loan you start, the more dramatic the savings, because every dollar of principal you knock down avoids years of compounded interest.

Should I pay off my mortgage early or invest?

Pure math says invest. At a 7% mortgage rate, prepaying gives you a guaranteed 7% return (lower after-tax if you itemize). The S&P 500 has historically returned about 10% annualized, so investing the difference in a low-cost index fund typically wins over 20-30 years. But mortgage prepayment is risk-free, behaviorally easy, and reduces sequence-of-returns risk - especially valuable for people within ~10 years of retirement. Most advisors suggest a hybrid: max out tax-advantaged accounts (401k match, Roth IRA, HSA) first, then split extra cash flow between prepayment and taxable investing.

How does the biweekly mortgage payment trick work?

Instead of one full monthly payment, you pay half the monthly amount every 14 days. Because there are 52 weeks per year, 26 half-payments equal 13 full monthly payments - one extra payment baked in annually, applied entirely to principal. On a 30-year loan that typically shaves 5-6 years off the payoff and saves tens of thousands in interest. Watch out: some servicers charge $300-$500 setup fees or monthly service fees for 'official' biweekly programs. You can replicate the effect for free by paying 1/12 extra each month or making one full extra payment in any month you can afford it.

Will my lender apply extra payments to principal automatically?

Not always - this is the single biggest mistake homeowners make. Many servicers default to applying unscheduled payments toward the next month's interest or to a suspense account, which means your extra money sits idle and saves you nothing. Always (1) write 'apply to principal' on the check or use your lender's online 'principal-only' payment option, (2) verify on the next statement that the principal balance dropped by exactly the extra amount, and (3) check your loan note for any prepayment penalty (rare on modern conforming loans but possible on older or non-QM loans).

Does extra mortgage payment affect my tax deduction?

Yes, but probably less than you think. If you itemize on Schedule A, you deduct mortgage interest paid each year. Prepaying reduces the interest you pay, which reduces the deduction - so your effective after-tax interest cost is lower than your headline APR. At a 24% marginal federal bracket, a 7% mortgage has an after-tax cost of about 5.3% if you fully itemize the interest. Most homeowners post-2017 take the standard deduction ($14,600 single / $29,200 MFJ in 2024) and don't itemize at all, in which case the tax angle is irrelevant and prepayment savings are fully realized.

Mortgage Payoff Calculator (Extra Payments)

Mortgage Payoff Calculator (Extra Payments)

How Extra Mortgage Payments Work

Frequently Asked Questions

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