Generate a monthly amortization schedule that splits each payment into interest and principal, with the remaining balance after the payment. Enter the amount, fixed annual interest rate, and term, then set a first payment date if you want dated rows. Extra-payment options let you model a recurring principal payment or a payment in a specific month. Open the schedule to inspect every row, or download a CSV for your own spreadsheet. Calendar dates label the model; they do not change the interest calculation.
Worked formula check
The inputs come from CFPB installment-loan sample inputs. This check uses regular monthly periods, excludes the sample's odd first period and other charges, and calculates the outputs with the formula below. It is not a lender offer.
| Input or result | Value |
|---|---|
| Calculated payment 1: interest / principal / balance | $50.00 / $185.37 / $4,814.63 |
| Calculated payment 2: interest / principal / balance | $48.15 / $187.22 / $4,627.41 |
| Calculated payment 3: interest / principal / balance | $46.27 / $189.09 / $4,438.32 |
Read a row from left to right
Each row starts with a payment number and its modeled date. The payment amount includes the regular installment and any extra amount that applies to that month. Interest is calculated using the balance at the start of the monthly period. Principal is the payment minus that interest. The last column is the balance left after principal is subtracted. You can follow that last column into the next row to see how the calculation carries forward. The final row can have a smaller payment because the tool caps it at the balance plus that month's interest.
Set dates without changing the rate model
Choose the first payment date to anchor the schedule. Later rows keep the day of the month when possible. If the starting date is the last day of its month, later payments use month-end dates. A date that does not exist in a shorter month is capped at that month's last day. These labels follow the monthly timing convention described in CFPB Appendix J. The calculator treats monthly periods equally. It does not count the days between dates, add interest for a partial first period, or move dates for weekends or holidays. Use your actual contract schedule for those details.
Use the CSV as a calculation record
After a valid calculation, select Download CSV to save the payment numbers, dates, payment amounts, interest, principal, and remaining balances. The download is generated in your browser from the currently calculated schedule. It does not send your loan details to a remote service. Recalculate before downloading if you changed an input. Dollar amounts are rounded to cents in the CSV, while the calculation retains additional precision between rows. Adding rounded displayed cells can therefore differ slightly from rounding the total once. The file is intended for reviewing the modeled repayment path, rather than matching a lender's daily accounting ledger.
Compare a schedule with extra principal
Start with no extra payments and inspect the final row. Then add your planned recurring amount, or use the one-time payment field and payment-month field together. The regular installment stays fixed. A smaller balance reduces the next monthly interest calculation and can bring forward the final row. The result area compares interest and payment count against the original schedule. This comparison assumes that all additional amounts reduce principal after the current month's interest. It excludes prepayment charges and any lender practice that instead advances a future due date. Check the agreement and payment instructions before relying on the modeled schedule.
How it works
r = annual interest rate (%) / 100 / 12
P is the interest-bearing balance, n is the number of monthly payments, r is the monthly rate, and A is the scheduled payment. At a zero interest rate, A = P / n. Each month, interest = opening balance * r; principal = payment - interest; closing balance = opening balance - principal.
This is the regular-payment form of the actuarial relationship in CFPB actuarial formulas, Appendix J. The schedule retains full precision internally and rounds amounts only for display. The model uses a fixed rate and equal monthly periods. It excludes daily accrual, irregular first periods, missed payments, and prepayment charges.
Frequently asked questions
Can I generate a loan amortization schedule with extra payments?
Yes. Add a monthly extra amount or a one-time payment in a selected month. The schedule includes those additions and stops when the balance reaches zero.
Can I download the schedule for a spreadsheet?
Yes. Download CSV creates a local file with each payment number, date, amount, interest, principal, and ending balance.
Why does principal change from month to month?
The fixed installment is split between interest on the current balance and principal. As the balance changes, that split changes even when the regular installment does not.
Does the first payment date change interest?
No. Dates label equal monthly periods. The tool does not use daily accrual or add a partial first period.
Why might the last payment be smaller?
The calculator caps a payment at the remaining balance plus current monthly interest, then closes the schedule at a zero balance.