How to use
- Enter the amount, annual interest rate and term.
- Optionally add a monthly extra payment.
- Review the schedule and chart; export CSV.
Worked example
$200,000 at 6% for 30 years: $1,199.10 per month (final payment $1,200.14) and $231,677.04 total interest without extra payments (interest rounded to cents each month).
Supported formats and limits
| Input | Amount, annual rate, term, extra payments |
|---|---|
| Output | Payment, schedule (CSV), balance chart |
| Engine | Standard annuity formula; schedule rounded to cents each month with the final payment adjusted |
Limitations
- Assumes a fixed rate and monthly payments with the annual rate divided by 12; property tax, insurance and loan fees are not included.
Questions
How is the monthly payment calculated?
Payment = P × r ÷ (1 − (1 + r)^−n), where r is the annual rate ÷ 12 and n the number of months, rounded half-up to the cent. Each month's interest is rounded to the cent and the last payment is adjusted so the balance ends at exactly zero. $200,000 at 6% for 30 years is $1,199.10 a month.
How do extra payments work?
An extra monthly amount and a one-time lump sum (made with a payment number you choose) go straight to principal. The tool compares the schedule with and without them, showing the interest saved and how many months sooner the loan ends.
Does it include taxes, insurance or fees?
No. It covers principal and interest at a fixed rate only. Add escrow, insurance or fees separately, and check your lender's figures, which may use a different rounding or day count.
Guides
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