Intergtm

Loan Payoff Acceleration Calculator

See exactly how many months you cut off and how much interest you avoid by paying extra each month.

Inputs

%

Results update as you type, and the address bar keeps your numbers so the link you share reopens this exact calculation.

Total interest saved

$97,691

Detailed results
Months saved96
Payoff time with extra payment265
Payoff time (current payment)361
Total interest (current payment)$318,989

What this result means

Total interest saved: $97,691.

Adding the extra payment saves $97,691 in interest and cuts 96 months off the loan.

Accelerated Payoff Schedule

Month-by-month balance, interest, and principal with extra payment included.

Accelerated Payoff Schedule. 120 rows, first 12 shown.
MonthRemaining BalanceInterestPrincipal
1$249,574$1,354$426
2$249,146$1,352$428
3$248,716$1,350$430
4$248,283$1,347$433
5$247,848$1,345$435
6$247,410$1,343$437
7$246,970$1,340$440
8$246,528$1,338$442
9$246,083$1,335$445
10$245,636$1,333$447
11$245,187$1,331$449
12$244,735$1,328$452

How this is calculated

Monthly simulation: balance += balance × rate/12, then subtract (base + extra) payment until balance = 0.

Every dollar you pay above the minimum on an installment loan goes directly to principal, reducing the balance on which future interest is calculated. This compounding effect means small extra payments have an outsized impact over time.

Front-loading matters. Extra payments made early in a loan save the most interest because interest is calculated on a higher balance. An extra $200/month in year 1 of a 30-year mortgage saves more than $200/month in year 25.

One-time lump sums. This calculator models recurring extra monthly payments. For a one-time lump sum, apply it to principal and then recalculate your amortization. The interest savings from a lump sum are even more dramatic.

Biweekly payments. Another approach: pay half your monthly payment every two weeks. This creates 26 half-payments per year = 13 full payments instead of 12 — one extra payment annually, applied entirely to principal.

Assumptions

  • Monthly compounding: monthly rate = annual rate ÷ 12.
  • Extra payment applied in full to principal each month.
  • Current payment assumed to cover at minimum the interest due each period.
  • No prepayment penalties.
  • Simulation caps at 50 years (600 months).

Frequently asked questions

›Does the extra payment go to principal?

Yes — as long as you've paid the interest due for that period, any amount above the regular payment reduces the principal balance directly. This is crucial because interest is calculated only on the remaining balance. By paying down principal faster, each subsequent month's interest charge is lower, creating a compounding savings effect throughout the loan's life.

›Should I tell my lender to apply the extra to principal?

Absolutely. When submitting extra payments, explicitly specify 'apply to principal' or 'apply to principal only' — some loan servicers have confusing default settings that may apply excess toward future payments instead, or hold the money in escrow, neither of which saves you interest. Get written confirmation from your servicer that the extra payment was applied correctly.

›Is it better to invest the extra money?

It depends on your personal risk tolerance and rate assumptions. If your loan rate is 6.5% and you genuinely expect 8% from stock investments long-term, investing wins on expected return — but you also accept market risk and volatility. Loan payoff offers a guaranteed 6.5% 'return.' Financial planners typically recommend maximizing tax-advantaged retirement accounts first (401k, IRA), then paying extra on high-rate debt (credit cards, auto loans), then investing additional surplus.

›What about prepayment penalties?

Some auto loans and personal loans carry prepayment penalties — typically 1–3% of the remaining balance — to compensate the lender for lost interest. Check your loan agreement for 'prepayment penalty' or 'early termination fee' clauses. The good news: most federal student loans and mortgages in the US have zero prepayment penalties. If your loan does carry one, calculate whether the penalty cost exceeds the interest you'd save before committing to extra payments.

›Does this work for any loan type?

Yes — mortgages, auto loans, personal loans, and most student loans use the same amortization math. Extra principal paid early saves the most interest because it's applied to the highest outstanding balance. The only exceptions are federal student loans under income-driven repayment (IDR), where payment caps are set by income instead of a fixed amortization schedule, making extra payments less impactful.

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