Amortization Calculator
This amortization calculator does more than print a schedule. Enter your loan, then add an extra monthly payment, a one-time lump sum, or switch to biweekly, and it shows exactly how much interest you'll save and how many years you'll shave off, side by side with the original plan. The balance chart and full schedule update as you type.
- Extra-payment simulator
- Interest saved
- New payoff date
- Biweekly option
- Full schedule
Last updated July 15, 2026 Estimate only, not a loan offer Reviewed by the Calcowa finance team
Enter a loan, rate, and term above 0.
What is loan amortization?
Amortization is the process of paying off a loan with equal, regular payments, where each payment covers the interest due that period plus a slice of the principal. The payment stays the same, but the split changes: at the start most of it is interest because the balance is large, and near the end almost all of it is principal. An amortization schedule is just the full list of those payments, and it's the clearest way to see where your money actually goes and how extra payments rewrite the ending.
How an amortization schedule is built
Here's the method the calculator runs, for a $300,000 loan at 6% over 30 years:
- 1
Find the fixed paymentM = P × r(1+r)ⁿ ÷ ((1+r)ⁿ − 1) with P = $300,000, r = 0.5% a month, n = 360 gives about $1,799.
- 2
Split the first paymentInterest is $300,000 × 0.5% = $1,500, so only $299 goes to principal in month one.
- 3
Reduce the balance and repeatThe new balance is $299,701. Next month the interest is slightly less, so a bit more goes to principal, and so on for 360 months.
- 4
Add any extra paymentsExtra money is added straight to the principal each month, which ends the schedule early and cuts the total interest.
How much extra payments save
On that same $300,000 loan at 6% over 30 years, here's what different strategies do. The change is dramatic because early payments are almost all interest, so attacking the principal early stops years of future interest. Try your own numbers in the tool above.
| Strategy | Payoff time | Total interest | Interest saved |
|---|---|---|---|
| No extra | 30 yr 0 mo | $347,515 | $0 |
| +$100/mo | 25 yr 8 mo | $286,779 | $60,736 |
| +$200/mo | 23 yr 1 mo | $256,204 | $91,311 |
| +$500/mo | 18 yr 4 mo | $196,364 | $151,151 |
| Biweekly | 25 yr 8 mo | $286,779 | $60,736 |
Weighing extra payments against investing? The compound interest calculator shows what the same money could earn instead, and the mortgage calculator adds taxes and insurance for a home loan.
Your amortization schedule
This schedule reflects your plan above, including any extra payments. Each row is one year: the interest and principal paid, and the balance left at year end. Watch how much faster the balance falls once extra payments kick in.
| Year | Interest | Principal | Balance |
|---|
Why biweekly payments work
Switch the toggle to biweekly and you'll see the schedule shorten without changing your monthly budget much. The reason is simple arithmetic: there are 52 weeks in a year, so paying half your monthly amount every two weeks makes 26 half-payments, which equals 13 full payments instead of 12. That hidden 13th payment goes entirely to principal. Over a 30-year loan it usually trims four to six years and saves tens of thousands, and it costs you nothing extra beyond that one payment a year. Just make sure your lender applies each half-payment right away rather than holding it until the full amount arrives.
Frequently asked questions
Is this amortization calculator free?
Yes, it's free and runs on any device with no sign-up. The figures are estimates to help you plan, not a loan offer, so your lender's exact numbers may vary a little with fees and rounding.
It's a month-by-month (or year-by-year) table showing how each loan payment splits between interest and principal, and how the balance falls to zero. Early payments are mostly interest because interest is charged on the whole remaining balance. As the balance drops, more of each payment goes to principal. This amortization calculator builds the full schedule and, unlike most, also simulates extra payments so you can see the payoff date move.
Every extra dollar goes straight to principal, so you stop paying interest on it for the rest of the loan. That shortens the schedule from the end and compounds: a smaller balance means less interest next month, which means more of your regular payment attacks principal too. On a $300,000 loan at 6% over 30 years, adding $200 a month pays it off almost 7 years early and saves about $91,000 in interest.
Yes, modestly, and painlessly. Paying half your monthly amount every two weeks means 26 half-payments a year, which equals 13 full monthly payments instead of 12. That extra payment goes entirely to principal and typically cuts four to six years off a 30-year loan. The calculator models this as one extra payment spread across the year, so the biweekly result matches the accelerated-biweekly method lenders use.
It helps most when applied early, because early in the loan the balance (and the interest it generates) is largest. A $10,000 lump sum in year two of a 30-year mortgage saves far more than the same $10,000 in year twenty. Use the one-time field to test a bonus, tax refund, or windfall and watch the interest-saved figure and payoff date update.
The fixed monthly payment is M = P × r(1+r)ⁿ ÷ ((1+r)ⁿ − 1), where P is the loan, r is the yearly rate divided by 12, and n is the number of months. Each month, interest is the balance times r, and principal is the payment minus that interest. Subtract the principal from the balance and repeat. Extra payments simply add to the principal portion each month.
It depends on the rate. Paying off a 6% loan is a guaranteed 6% return, tax-free of risk. Investing might earn more over the long run but isn't guaranteed. Many people split the difference: keep a small emergency fund, capture any employer retirement match first, then decide between extra payments and investing based on your rate and comfort with risk. The compound interest calculator shows the investing side.
Related calculators
More tools for loans and planning.
Payment with taxes and insurance.
Loan calculatorAny fixed-rate loan.
Compound interest calculatorInvest the difference instead.
Paying off a loan?
Test an extra payment above, or browse the full finance hub.