Payment Calculator
Principal ($), Annual rate (%), and Term (months) feed the standard amortizing payment. Calculate Payment also lists the total of payments and the interest inside that total.
How to use
- Enter the amount borrowed in Principal ($). The sample is 20000. This box is the balance that accrues interest, not a price before a down payment.
- Enter a yearly percent in Annual rate (%). The sample is 6. The script divides by 100 and then by 12 to get the monthly rate.
- Enter Term (months), not years. The sample is 36. A zero or empty term is treated as 1 month.
- Click Calculate Payment. The large line is dollars per month. The detail line is Total of payments and Interest.
When it helps
Use it for a fixed personal loan, an equipment note, or any installment where you already know the principal and the term is stated in months. Interest on the detail line is total of payments minus principal, so you can see the cost of the rate without building a row for every month.
The loan calculator uses the same payment math with labels Loan amount ($), Interest rate (%), and a Calculate button. The interest calculator does not amortize: it prints simple interest beside once-a-year compound interest and never a monthly payment.
Limits
No extra fees. The form does not ask for origination, late charges, insurance, taxes, or an added balloon. A zero Annual rate (%) sets the payment to principal divided by the month count, so interest comes out at zero. Any other rate uses the standard payment formula: principal times monthly rate times (1 + monthly rate) to the term, divided by that same power minus one.
The result is arithmetic, not a lender quote. Extra principal payments, a skipped month, and a rate that changes mid-term are outside the form. Total of payments is the level payment times Term (months), including the last month, with no separate fee tacked on.
Questions
Is Term (months) the same as years times 12?
You have to do that conversion yourself. A five-year note is 60 in Term (months). The field is not labeled in years, and the script does not multiply it by 12.
What is included in Interest?
Only the gap between total of payments and Principal ($). Points, a document fee, or prepaid interest are not asked for, so they are not inside that gap.
Does a 0 percent rate break the formula?
No. The script checks for a zero monthly rate and divides principal by the month count instead of using the power formula. Click Calculate Payment after setting Annual rate (%) to 0 to see a payment with no interest.