ToolPetal
Loan calculator
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| Year | Principal paid | Interest paid | Balance at year end |
|---|
Full payment schedule (CSV text)
Client-side only. Fixed-rate, monthly-payment estimate with interest charged monthly at one twelfth of the annual rate. Not a loan offer, and your lender's schedule is the one that counts.
Where the money goes on a $300,000, 6.5%, 30-year loan
Big loans make the shape of amortization easy to see. The payment is $1,896.20 a month, fixed for 360 months. The first payment splits like this:
| Milestone | What happens |
|---|---|
| Payment 1 | $1,625.00 interest, $271.20 principal |
| Payment 180 (year 15) | Balance still $217,678.77, about 73% of the original |
| Payment 233 | First month where principal ($949.69) beats interest ($946.51) |
| Payment 257 | Balance finally drops below half, $150,000 |
| Payment 360 | Balance hits zero. Total interest paid: $382,636.71 |
So the interest over the full term is about 1.28 times the amount borrowed. Halfway through the term you have repaid roughly a quarter of the principal. That is not a trick, it is arithmetic: interest is charged on whatever you still owe, and in the early years you owe almost all of it.
Shortening the term to 15 years at the same rate lifts the payment to $2,613.32 and cuts total interest to $170,398.28. The payment goes up by $717.12 a month, and total interest falls by $212,238.43.
Same $20,000 at 7%, three term lengths
The cheaper monthly payment is the one that costs more. Here is a personal or car loan at three terms:
| Term | Monthly payment | Total interest | Total paid |
|---|---|---|---|
| 3 years | $617.54 | $2,231.50 | $22,231.50 |
| 5 years | $396.02 | $3,761.48 | $23,761.48 |
| 7 years | $301.85 | $5,355.80 | $25,355.80 |
Going from 5 to 7 years saves $94.17 a month and costs $1,594.32 more overall. Whether that is a good trade depends on what the $94.17 does elsewhere. If it only stretches a tight budget, it may be worth it. If a longer term lets you buy a bigger car, it probably is not.
The rate matters too. On the same 5-year, $20,000 loan, 6% gives $386.66 a month and $3,199.35 of interest, while 8% gives $405.53 and $4,331.62. Two points of rate is about $1,132 over the life of the loan.
Extra payments, tested on the 5-year loan
| Extra per month | Months to pay off | Total interest | Interest saved |
|---|---|---|---|
| $0 | 60 | $3,761.48 | none |
| $50 | 53 | $3,253.07 | $508.41 |
| $200 | 38 | $2,322.67 | $1,438.81 |
The last payment is smaller than the rest, because it only needs to clear what is left. On the $300,000 loan, an extra $200 a month ends it after 277 payments instead of 360, 83 months early, and saves $103,450.19 of interest. Before you rely on this, check that your lender applies extra money to principal right away and does not charge a prepayment penalty. Some hold it as an early payment toward next month's bill instead.
Left out on purpose
- Escrow and mortgage extras. Property tax, homeowner's insurance, mortgage insurance and HOA dues are added to a real mortgage bill. This page shows principal and interest only.
- Fees. Origination fees, points and closing costs are not part of the payment. Rolling them into the loan amount is how you include them.
- Variable and promotional rates. Adjustable-rate loans, interest-only periods and teaser rates change the schedule. This page holds one rate for the whole term.
- Daily interest. Some auto and personal loans accrue interest daily, so paying late or early shifts a few dollars. A monthly model will differ from your statement by small amounts.
- Rounding. Payments are rounded to cents and the final payment absorbs the leftover. Your lender may round slightly differently.
- Balloon payments, deferment and irregular payments. Not modelled. Student loans with deferment in particular need the servicer's schedule.
FAQ
Is this a loan calculator or a mortgage calculator?
Both, as far as the payment math goes. A fixed-rate mortgage uses the same level-payment formula as a car or personal loan. What a mortgage adds on top (property tax, home insurance, mortgage insurance, HOA dues) is not in this page, so the payment shown here is principal and interest only.
What interest rate should I enter, the rate or the APR?
Enter the nominal annual rate printed on the loan quote. This page divides it by 12 and charges that each month. APR folds fees into a single yearly figure, so putting the APR in here overstates the monthly payment slightly and includes fee cost that you may have paid up front instead.
How do extra payments change the result?
The extra amount is added to every monthly payment and goes straight to principal. Because next month's interest is charged on a smaller balance, the loan ends sooner and total interest drops. The page shows the payoff date and the interest saved compared with paying the minimum.
Why is almost all of the first payment interest?
Interest each month is the balance times the monthly rate. At the start the balance is at its highest, so interest is at its highest, and the fixed payment leaves only a small remainder for principal. Each month the balance shrinks a little, so the split slowly tilts the other way.
Does this work for a 0% loan?
Yes. At 0% the payment is the amount divided by the number of months, and total interest is zero. Watch for promotional 0% offers that charge interest retroactively if the balance is not cleared in time. That rule is not modelled here.
Is my loan information uploaded?
No. The numbers you type are used in this browser tab only. Nothing is sent to ToolPetal or kept after you close the page.