Amortization Calculator
Loan amount ($), Interest rate (%), and Term (years) feed Generate Schedule, which converts the years to months and splits each counted payment into principal and interest.
How to use
- Enter Loan amount ($). The sample is 200000.
- Enter a yearly percent in Interest rate (%). The sample is 6.5. The monthly rate is that percent divided by 100 and then by 12.
- Enter Term (years). The sample is 30, and the box is marked with a maximum of 40. The script rounds years times 12 to get the month count.
- Click Generate Schedule. Above the grid, Monthly is the level payment and Total interest is that payment times the month count, minus the loan amount.
- Read the table columns in order: # (the payment number), Payment, Principal, Interest, and Balance.
When it helps
Use it to see early payments land mostly in Interest while Principal stays small, then later rows shift toward principal. The last row sets principal equal to the remaining balance so Balance can hit zero.
If you only need the monthly figure and not the grid, the loan calculator takes the term in months and stops at payment, total paid, and total interest. A purchase price minus a down payment, with the term in years, is the mortgage calculator, which does not draw this table.
Limits
The math is monthly, but a long table is abbreviated. From 31 months upward the grid prints payments 1 through 24, an ellipsis, each later payment number divisible by 12, and the final six payments. Months left out of the grid still feed Monthly and Total interest. At 30 months or fewer, every payment is listed.
The form does not ask for taxes, insurance, extra principal, or a rate change. These figures are arithmetic, not a lender quote or a servicer statement, and there is no export button. Term (years) is marked with a maximum of 40.
Questions
Why are some payment numbers missing?
After payment 24 the script skips ahead. It keeps a row when the payment number divides evenly by 12, and it always keeps the last six. The ellipsis is one cell spanning the five columns. That is a display cut, not a skipped bill in the math.
Does Term (years) stay in years inside the formula?
No. Months equal years times 12, rounded. A term of 30 is 360 months in the math even when most rows are not drawn.
What does the last Payment cell do differently?
On the final month, principal is set to the remaining balance and the payment becomes that principal plus the last interest charge. Earlier rows use the level payment printed as Monthly.