Amortized Loan Calculator: Payment Schedule & Extra Payments

An amortized loan is paid off with equal, scheduled payments, each split between interest and principal. Enter a loan amount, rate, term, and payment frequency to see the payment, the full schedule, and what extra payments would save.

The short answer: a $250,000, 30-year loan at 6.75% has a monthly payment of $1,621.50 and costs about $333,738 in interest over its life. Adding $200 a month to principal pays it off 8 years early and saves about $103,600. The calculator shows those numbers for any loan, along with a payment-by-payment schedule.

This calculator is for informational purposes only, and its results are estimates. Your lender's figures may differ slightly because of rounding, payment dates, and fees.

What each input means

How the payment is calculated

The calculator divides the annual rate by the number of payments per year to get the periodic rate (r), and multiplies the number of years by payments per year to get the number of payments (n). Then:

Payment = P × r(1 + r)^n ÷ [(1 + r)^n − 1]

For $250,000 at 6.75% paid monthly for 30 years:

• r = 0.0675 ÷ 12 = 0.005625
• n = 360
• Payment = $1,621.50

Each period, interest = remaining balance × r. The rest of the payment goes to principal. Any extra payment goes entirely to principal, which shrinks next month's interest and shortens the loan.

Worked example: the first payments on a $250,000 mortgage

Payment 1 interest: $250,000 × 0.005625 = $1,406.25. Principal: $1,621.50 − $1,406.25 = $215.25.

Over the first full year, you pay $19,458 in total, but only $2,664 of it reduces the balance; $16,794 is interest. Principal doesn't exceed interest in a payment until payment 238, almost 20 years in. That front-loading is why extra payments early in a loan are so powerful.

What extra payments save

Same loan: $250,000, 6.75%, 30 years, monthly.

The extra payment that saves the most is the one you can sustain. Before prepaying a mortgage, make sure you have an emergency fund and no high-rate debt, since a credit card at 22% is a better target than a mortgage at 6.75%. The debt cost calculator ranks what your balances cost.

When you send extra money, tell the servicer to apply it to principal. Otherwise some servicers hold it as an advance on next month's payment, which saves nothing.

One-time lump sums

You don't need a monthly commitment to make a difference. A single $10,000 payment toward principal at the end of the first year on the same loan cuts about 3 years (38 payments) off the schedule and saves about $53,200 of interest. The calculator models recurring extra payments, so for a one-time lump sum, subtract it from the loan amount and shorten the term to match the remaining payments shown in the schedule.

How much does the interest rate change the payment?

Small rate differences add up over a long loan. Here is the same $250,000, 30-year loan at different rates:

Each half-point costs roughly $80 to $85 a month and about $30,000 over 30 years. That's why comparing offers from several lenders, or paying points to buy the rate down when you'll keep the loan long enough, can be worth more than many years of extra payments.

Does payment frequency matter?

This is where many calculators and articles mislead. The tool's frequency setting divides the annual rate and the payment by the number of payments per year and keeps the same term. Paying more often then saves very little, because you pay the same yearly amount:

The difference between monthly and daily is under $500 over 30 years.

The real savings from a biweekly plan come from paying half the monthly payment every two weeks: 26 half-payments equal 13 monthly payments a year. On this loan that's $810.75 every two weeks, which pays it off about 6 years early and saves about $79,600. To model it in the calculator, keep the frequency on monthly and enter one-twelfth of the payment ($135.13) as an extra monthly payment.

Before signing up for a lender's or third party's biweekly program, check for setup or per-payment fees and confirm the money is applied when received, not held until a full payment builds up.

Typical uses and terms

Interest-only loans, credit cards, and HELOCs in their draw period aren't amortized, so this calculator won't match their payments. Balloon loans amortize on a long schedule but come due early, so use the schedule's balance at the balloon date to see what you'd owe.

Reading the amortization schedule

Each row of the schedule shows:

• Payment number in order.
• Payment, which includes any extra principal.
• Interest charged for that period on the starting balance.
• Principal, the part that reduces the debt.
• Balance after the payment.

Three things to look for:

1. The crossover point, when principal first exceeds interest. Prepaying before it has the biggest effect.
2. Your balance at a planned sale or refinance date. If you might move in seven years, the schedule tells you roughly what you'll still owe. On the base example, that's about $227,000 after seven years of scheduled payments.
3. The final payment, which is often slightly smaller because of rounding.

Should you refinance or prepay?

Prepaying is a guaranteed return equal to your loan's rate. Refinancing changes the rate itself but comes with closing costs. Run both:

• Use this calculator with your current balance and remaining months to see the cost of staying put, with and without extra payments.
• Use the mortgage refinance calculator to compare a new rate after closing costs and find the break-even month.

If you're still deciding how much to borrow in the first place, the loan affordability calculator works backward from the payment your budget can carry.

Tax angles worth knowing

• Mortgage interest is deductible only if you itemize, on up to $750,000 of acquisition debt for loans taken after December 15, 2017. With the 2026 standard deduction at $32,200 for joint filers, many homeowners don't itemize.
• Car loan interest on a new, U.S.-assembled vehicle bought for personal use can be deductible up to $10,000 a year from 2025 through 2028, with income limits. The car loan interest deduction calculator estimates it, and the amortization schedule gives you each year's interest.
• Student loan interest is deductible up to $2,500 a year, subject to income limits.