Loan Payoff Calculator

How this loan payoff calculator works

The math behind this calculator is standard installment-loan amortization, run one month at a time. Each month, interest accrues on whatever balance is left, at your annual rate divided by 12. The rest of your payment (payment minus that month's interest) goes toward the principal, and the balance drops by that amount. Repeat that every month, and you get your exact payoff date and the total interest you will pay over the life of the loan.

Add an extra payment each month and the calculator adds that amount to the principal portion every single month, which snowballs: a smaller balance means less interest accrues the following month, which means even more of next month's payment goes to principal. A one-time extra payment works the same way but only once, applied to principal the first month you run the calculation. Either way, the calculator runs a second, baseline version of the same loan with no extra payments at all, so it can show you exactly how much time and interest your extra payments are actually saving, not just the with-extra numbers on their own.

Three worked examples

A few real scenarios, using the same math the calculator runs, so you can sanity-check your own numbers before you rely on them. The auto loan example below uses the same engine as the car loan payoff calculator, which has defaults already tuned for a typical auto loan:

1. Auto loan: $22,000 balance, 6.9% APR, $450/month payment, no extra payments. Payoff in 4 years 10 months, about $3,900 in total interest over the life of the loan.
2. Personal loan with extra payments: $12,000 balance, 11.5% APR, $300/month payment plus a $100 extra payment every month. Without the extra payment that loan takes 4 years 3 months to pay off; with it, 3 years flat, about 15 months faster, and close to $1,000 less in total interest.
3. Mortgage with a one-time lump sum: $310,000 balance, 6.25% APR, $1,950/month payment, plus a single $15,000 extra payment applied today (say, from a bonus or a tax refund). That one lump sum alone cuts more than 3 years off a roughly 28-year payoff schedule and saves over $60,000 in interest, because it reduces the balance interest accrues on for every remaining month of the loan.

Why extra payments save more than they look like they should

An extra $100 a month does not just subtract $100 from what you would have owed, it changes how much interest accrues on everything after it. Every dollar that goes to principal early stops accruing interest for every remaining month of the loan, not just the month you paid it. That is why a relatively small, consistent extra payment early in a loan's term (when the balance, and therefore the interest charge, is highest) tends to save more than the same extra payment made later, once the balance is already smaller. It is also why a single early lump sum on a long loan like a mortgage can outperform a much larger total amount paid in small increments near the end.

Reading your amortization schedule

The year-by-year table below the calculator shows exactly how your specific numbers play out: how much of each year's payments went to interest versus principal, and what your ending balance looks like at the close of each year. Early in most loans, a surprisingly large share of each payment goes to interest rather than principal, since interest is calculated on the full remaining balance. As the balance drops, that ratio flips, and more of each payment chips away at principal. Watching this table with and without extra payments entered is often the clearest way to see why extra payments matter more than the raw dollar amount suggests, especially in a loan's earlier years.

Extra payments vs. refinancing

Making extra payments and refinancing solve a similar problem (paying less interest over time) in different ways. Refinancing replaces your loan with a new one, usually to get a lower rate or change the term, but it typically comes with new closing costs or fees and resets some of the loan's early, interest-heavy amortization. Extra payments keep your original loan and rate exactly as they are, and simply accelerate how fast the principal goes down, with no fees and no new paperwork. If your rate is already competitive, extra payments are usually the simpler way to cut interest; if rates have dropped significantly since you took out the loan, it is worth comparing what a refinance would cost against what this calculator shows you could save just by paying extra on the loan you already have.

Biweekly and weekly payment strategies

A common way to accelerate payoff without much budget impact is switching from monthly to biweekly payments, half your monthly payment every two weeks. Since a year has 52 weeks, that works out to 26 half-payments, the equivalent of 13 full monthly payments a year instead of 12, one extra payment snuck in almost painlessly. To model that effect here, take your monthly payment, divide it by 12, and enter that amount in the extra payment each month field, this calculator will show you the same payoff acceleration a true biweekly plan would give you, without needing a separate weekly or biweekly mode. If your lender charges a fee for a formal biweekly payment plan, doing the math yourself this way and simply paying extra each month achieves the same result for free.

What if my payment does not cover the interest?

If the monthly payment you enter is lower than the interest accruing on your current balance, the loan will never pay itself off, the balance would actually grow instead of shrink. This calculator catches that case and tells you directly rather than showing a misleading result: you will need either a higher regular payment, or extra payments large enough to make real progress on principal. This situation comes up most often with interest-only or minimum-payment credit structures, worth double-checking your actual required payment against your statement if you see this message.

How to actually start making extra payments

Deciding to pay extra is the easy part, making sure the extra money actually reduces your principal is where people run into friction. A few practical steps that apply to most lenders:

• Confirm your lender applies extra payments to principal by default. Some loan servicers apply anything above the scheduled payment to next month's payment instead, which does not shrink your balance the same way, check your account settings or call and ask specifically for "principal-only" or "additional principal" payments.
• Label the extra amount clearly if you are mailing a check or using a payment portal that has a separate field for extra principal, use it, rather than just writing a larger total on one combined payment.
• Set up extra payments as automatic if your budget allows it. A recurring $50-100 extra payment that happens automatically tends to survive far longer than a manual one you have to remember to make every month.
• Recheck the numbers here whenever your rate or payment changes, an adjustable-rate loan, a refinance, or a change in your regular payment amount all shift the payoff date and interest total this calculator gives you.
• Keep an eye on your statement's principal balance after the first extra payment posts, confirming it actually dropped by the extra amount (not just the scheduled principal portion) is the simplest way to verify your lender applied it correctly.