15 Year Loan Calculator

What a 15 year loan schedule looks like

A 15 year loan is any loan repaid over 180 monthly payments at one rate. Car loans, personal loans, RV and boat loans, land loans and home improvement loans can all be written on that schedule, and they all amortize the same way: one level payment, a balance that falls slowly at first and faster later.

Take $50,000 at 9.5 percent APR. The monthly rate is 0.095 / 12 = 0.0079167, the payment is $522.11, and 522.11 x 180 = 93,980 in total payments. Of that, 93,980 - 50,000 = 43,980 is interest.

Three numbers decide everything: the amount borrowed, the rate and the 180 month term. Change any one and the payment moves. A 15 year term is long for a vehicle and short for a mortgage, which is why the same arithmetic serves products as different as a boat and a kitchen remodel.

The calculator above takes any amount and rate, adds an optional extra payment, and returns the payment, the interest cost and the payoff time in months and years.

The amortization math behind the calculator

The payment comes from the standard amortization formula: the balance times the monthly rate, times a growth factor, divided by that growth factor minus one. The growth factor is 1 plus the monthly rate raised to the 180th power.

Run the $50,000 example at 9.5 percent. The monthly rate is 0.0079167, so interest on the full balance in month one is 50,000 x 0.0079167 = 395.83. The growth factor works out to 4.1346, which turns into a multiplier of 1.31907, and 395.83 x 1.31907 = 522.11.

That first payment splits almost three to one. Interest takes 395.83 and principal takes 522.11 - 395.83 = 126.28. Put another way, 395.83 / 522.11 = 0.758, so about 76 percent of payment one is interest and 24 percent reduces the debt.

Every later payment splits a little better, because interest is charged on a smaller balance each month. The payment stays at 522.11 while the mix inside it rotates, and the crossover where principal finally beats interest comes at payment 94.

Term trade-offs on the same $50,000

The term is the lever most borrowers can pull. Here is the same $50,000 at 9.5 percent spread across four common schedules.

Going from 60 months to 180 months cuts the payment from 1,050.09 to 522.11, a saving of 1,050.09 - 522.11 = 527.98 a month. It also adds 43,980 - 13,006 = 30,974 of interest, which is more than half the amount borrowed.

The 180 month payment is 646.99 - 522.11 = 124.88 below the 120 month payment. That difference is the price of the last five years of the schedule, and it is the reason long terms sell: they make a larger purchase fit a monthly budget without changing the sticker price.

A middle option often works better than either extreme. A 120 month loan keeps interest at 27,639 while holding the payment near 647, which is 16,341 less interest than the 15 year schedule.

What an extra $100 a month does

Extra principal is the cheapest way to shorten a 15 year loan, because the payment is already set and the lender has no reason to reprice it. Add 100 to the 522.11 payment and the borrower sends 522.11 + 100 = 622.11 a month.

The loan closes after 129 payments instead of 180: 180 - 129 = 51 payments skipped, so the term drops from 15 years to 10 years and 9 months. Interest falls from 43,980 to 29,789, a saving of 43,980 - 29,789 = 14,191. That is 14,191 / 43,980 = 0.323, or about 32 percent of the interest, bought with 100 a month for under 11 years.

The mechanism is simple. Every extra dollar lowers the balance, and a lower balance is charged less interest next month, so a larger share of the regular payment goes to principal from then on. The effect compounds quietly rather than dramatically, which is why the saving shows up as years and thousands rather than as a lower payment.

Two practical notes. Check the contract for a prepayment penalty before sending extra money, since the Consumer Financial Protection Bureau notes that some loans charge one. Then tell the servicer in writing that the extra amount is for principal, or it may be applied to next month's payment instead.

Where a 180 month term shows up

Most auto lenders stop at 72 or 84 months, and the average new car loan ran 69.5 months in the second quarter of 2026, according to Experian's auto finance data. A 15 year term on a car is unusual, and it usually means a shopper traded term for payment on a vehicle that will not last the schedule.

The 180 month term is normal in other places: recreational vehicles, boats, land, manufactured housing, some home improvement loans and secured personal loans. Those purchases hold value longer or are attached to something that does, so a long amortization makes more sense than it does on a sedan.

Depreciation is the risk to watch. A $50,000 vehicle loses value fastest in the first three years, and if the balance falls slower than the resale value, the owner is upside down and cannot sell without writing a check. The same balance on a boat or a piece of land usually tracks its collateral more closely.

The CFPB auto loan guide covers the paperwork side: the loan estimate style disclosures, add-on products and the trade-in arithmetic.

How your rate changes the total

Rate does more work than most borrowers expect on a 180 month schedule, because interest is charged on a large balance for a long time. Here is the same $50,000 at three rates that bracket the current market.

Moving from 6.35 percent to 11.19 percent raises the payment by 574.28 - 431.44 = 142.84 a month and the interest by 53,370 - 27,659 = 25,711. That spread is why credit repair and a rate shopping pass matter more than a small discount on the purchase price.

Experian's second quarter 2026 data shows the full ladder: new car APRs averaged 4.41 percent for super prime borrowers and 16.11 percent for deep subprime, with used car averages running 2 to 5 points higher at every tier.

Watching the balance fall

An amortization table looks slow at the start and fast at the end, and that shape is the single most useful thing to understand about a 15 year loan.

After five years, 50,000 - 40,349 = 9,651 of the original balance is gone, which is under a fifth of the loan. The halfway point arrives in year 10, not year 7.5, because interest takes the larger share of every early payment.

This is why a 15 year loan feels stuck to a borrower who sells in year 4, and why the same loan feels fast in year 12. It is also why extra principal has an outsized effect early: money sent in year 2 removes interest from 13 more years of payments.

What this calculator leaves out

The payment covers principal and interest only. Origination fees, documentation fees, title work and dealer charges are paid separately or rolled into the amount financed, which changes the balance rather than the rate.

The APR and the note rate are not the same number. The APR folds in fees and is the right figure for comparing offers, while the note rate is the one that builds the payment shown here. Enter the note rate when you want the payment, and compare APRs when you want to know which loan is cheaper.

Add-on products are outside the math as well. Gap insurance, credit life insurance, extended warranties and payment protection plans are often sold alongside a long loan, and each one either raises the amount financed or adds a monthly charge.

Finally, the calculator assumes a fixed rate and a simple interest loan with on-time payments. Variable rate personal loans, precomputed interest contracts and late fees all change the outcome.

Use the output as a planning estimate. Confirm the payment, the APR and any fees on the disclosure the lender provides before signing.