How to use the amortization schedule calculator
- Enter the Loan amount, Interest rate (%) and Loan term (years). It works for mortgages, car loans and personal loans with fixed monthly payments.
- Add an Extra monthly principal amount to see how much interest and time extra payments save, or leave it at 0.
- Set the First payment date so the schedule and Payoff date line up with your calendar.
- Switch between Monthly and Yearly views, then use Download CSV for a spreadsheet or Print for a paper copy.
How amortization is calculated
The monthly payment is M = P × r / (1 − (1 + r)−n), where P is the loan amount, r is the yearly rate divided by 12 and n is the number of payments, rounded to the cent. Each month, interest is the remaining balance times r, and the rest of the payment (plus any extra) reduces the balance. Because the payment and each month's interest are rounded to the cent, the final payment differs slightly from the others so the balance ends at exactly $0.00, which is how lenders handle rounding. The CFPB's amortization explainer describes the same process.
Worked example with the default numbers
A $300,000 loan at 7% for 30 years has a monthly payment of $1,995.91. In payment 1, interest is $300,000 × 7% / 12 = $1,750.00, so only $245.91 goes to principal and the balance falls to $299,754.09. Over 360 payments you pay $418,524.05 in interest and $718,524.05 in total, with a final payment of $1,992.36. Principal overtakes interest at payment 242, about 20 years in. Enter $200 in Extra monthly principal and the loan is paid off in 275 payments, 7 years 1 month early, saving $116,638.28 in interest.
Limits and edge cases
- Fixed-rate, monthly payment loans only. Adjustable-rate, interest-only and biweekly loans follow different schedules.
- The payment is principal and interest. Escrow for property tax and insurance is not included; the mortgage calculator adds those.
- Extra principal is applied every month from the first payment. Your servicer's statement may differ by a few cents because of day-count rules.
- Terms with part-years are rounded to whole months, so 2.55 years becomes 31 payments.
- To see how a new rate would change this schedule, try the mortgage refinance calculator.
Amortization FAQ
How much of my mortgage payment goes to interest?
Early on, most of it. On a $300,000 loan at 7% for 30 years, the first payment of $1,995.91 includes $1,750.00 of interest, about 88%. The interest share falls every month as the balance shrinks.
When does principal overtake interest on a 30-year loan?
Around year 19 to 21 at rates of 6 to 7%. At 7% it happens at payment 242; at 6.5% it happens at payment 233.
How do extra payments change my schedule?
Every extra dollar goes straight to principal, so later payments carry less interest and the loan ends sooner. Adding $200 a month to the default loan saves $116,638.28 and finishes 85 payments early. Ask your servicer to apply extra money to principal.
Can I use the schedule for my mortgage interest deduction?
The Yearly view estimates interest paid in each calendar year, but your lender's Form 1098 is the figure to use. For 2026 the deduction covers interest on the first $750,000 ($375,000 if married filing separately) of home debt taken out after December 15, 2017, a limit the 2025 tax law made permanent, and only if you itemize.
Paying off a car or personal loan instead? The loan payoff calculator shows how fast a set monthly amount clears it.
Sources: CFPB, What is amortization; IRS Publication 936 (2025), Home Mortgage Interest Deduction.