Loan Payoff Calculator

Why extra payments punch above their weight

Your regular monthly payment does two jobs: first it covers the interest your balance generated that month, and only whatever is left over reduces the balance itself. Early in a loan, the interest job eats most of the payment. An extra payment is different — the interest bill is already paid, so every extra dollar goes 100% to principal.

That’s only half the story. Each dollar of principal you remove stops generating interest for the loan’s entire remaining life. Pay $100 extra on a 9.5% loan with four years left, and you don’t just save $9.50 — you save roughly 9.5% of $100 compounding for four straight years, because your later payments now attack a smaller balance, which shrinks the next month’s interest, which frees more of the following payment for principal, and so on. Prepaying a loan is compound interest running in your favor for once.

This is also why early extras save the most. An extra $500 in month 3 spends years suppressing interest; the same $500 in the final year barely has time to work. If you’re going to accelerate a loan, the best month to start is this one.

Extra monthly vs. one-time lump sum

Both help, and the calculator above lets you test each — or combine them. The lump sum (a tax refund, a bonus) delivers an immediate, satisfying drop in the balance. The extra monthly amount looks small by comparison but keeps chipping away every single month.

Run the default numbers and you’ll see the pattern: on an $18,000 balance at 9.5% APR with a $380 payment, the loan takes about 5 years and roughly $4,600 in interest on its own. Adding $100 every month pays it off about 15 months sooner and saves around $1,200 of that interest. A one-time $1,200 (the same total dollars as a year of $100s) shaves about 5 months and $650 — it helps, but less, because it only goes to work once, while the monthly extra keeps recommitting new money that would otherwise leak away. Over the life of a loan, regular small extras usually beat rare large ones, simply because consistency puts more total dollars against principal. The unbeatable move, if you can manage it, is both.

The order to send extra money

If you carry more than one debt, resist the urge to sprinkle extra money across all of them. Mathematically, every spare dollar should go to the highest-APR debt first while you make minimums on the rest — that’s where each dollar cancels the most interest. A 24% credit card outranks a 9% personal loan, which outranks a 6% auto loan. If credit cards are in the mix, our credit card payoff calculator handles multiple cards and compares payoff orders directly.

Two practical checks before your first extra payment:

• Check for prepayment penalties. Most modern loans don’t have them, but some auto and personal loans do — especially ones with precomputed interest, where the total finance charge is fixed up front and prepaying saves little. One look at your loan agreement (search for “prepayment”) settles it.
• Make sure the extra hits principal. Some lenders’ default is to treat extra money as an early next payment — which advances your due date but saves you almost nothing. When you pay online, look for an “apply to principal” option; if you mail a check or use your bank’s bill pay, write “apply to principal” in the memo, and verify on your next statement that the balance dropped by the full extra amount.

Should you pay off the loan early at all?

Honest answer: not always. Prepaying a loan is an investment with a guaranteed return equal to the loan’s APR — so compare that APR to what the money could earn elsewhere.

• Emergency fund first. Extra loan payments are a one-way door: once sent, you can’t get the money back without borrowing again, often at a worse rate. Before accelerating anything, keep several months of expenses in savings.
• High-rate debt is a guaranteed win. Paying down a loan at 9%, 15%, or 24% is a risk-free, tax-free return at that rate. No savings account or predictable investment matches it, so high-APR balances deserve every spare dollar.
• Low-rate loans are genuinely arguable. If your loan sits under roughly 4–5%, money in a high-yield savings account or a diversified investment may reasonably earn more than the loan costs. Plenty of people prepay anyway for the peace of mind of owing nothing — that’s a legitimate choice, just know it’s an emotional return, not a mathematical one.

Two related situations deserve their own tools. Mortgages bring extra wrinkles — long horizons, possible tax effects, escrow — so use our mortgage payoff calculator for those. And if the real problem is the rate itself rather than the balance, refinancing or consolidating may beat brute-force prepayment; our debt consolidation calculator shows whether a lower-rate loan actually saves money after fees.

The biweekly trick: a 13th payment hiding in your calendar

Here’s a way to make an extra payment without ever feeling it. Instead of paying your monthly amount once a month, pay half of it every two weeks. It sounds like the same thing — but it isn’t. A year has 52 weeks, so you make 26 half-payments = 13 full payments, not 12. That quietly sneaks one entire extra payment into every year, timed to your paycheck if you’re paid biweekly like most US workers.

To see what it’s worth, divide your monthly payment by 12 and enter that number in the “extra monthly payment” field above — mathematically that’s almost exactly what a biweekly schedule does. On the calculator’s default loan it trims several months and hundreds of dollars, and on a mortgage the same trick removes years.

One warning: some lenders and third-party services sell “biweekly payment programs” with enrollment fees of $200–400 plus per-payment charges — for something you can do yourself for free. Either set up your own biweekly transfers (if your lender accepts partial payments) or simply add one-twelfth of your payment as a monthly extra, which achieves the same result with zero fees and no middleman.

Where the extra money comes from

An acceleration plan lives or dies on consistency, so anchor it to money that shows up reliably rather than willpower:

• Round up the payment. If your payment is $380, pay $400 or $450 — round numbers hurt less, and automating them means the decision happens once instead of every month.
• Commit windfalls in advance. Decide today that half of any tax refund, bonus, or cash gift goes to the target loan. The average US tax refund alone is a $3,000-class lump sum — enter it in the one-time field above to see what just one refund does.
• Redirect payments that end. When a subscription is cancelled or another loan is paid off, its old payment is money your budget already doesn’t miss. Rolling it into the target loan is the same “snowball” effect that makes multi-debt payoff plans accelerate.
• Keep the raise, pay the difference. A common compromise on pay raises: keep half for life, aim half at debt. You still feel the raise, and the loan still dies early.

Whichever source you use, rerun the calculator with the real number. Watching the payoff date jump closer — and the interest column shrink — is the most reliable motivation there is, because it’s your actual loan, not a hypothetical.

Disclaimer: This calculator is for educational purposes only and provides estimates based on the numbers you enter. It is not financial, legal, or tax advice. Actual loan terms, rates, and payments depend on your lender and personal circumstances. All calculations run in your browser — nothing you enter is stored or sent anywhere.