Calculate your monthly loan payment, total interest, and total cost for any fixed-rate loan. Includes a full year-by-year amortization schedule.
| Year | Principal Paid | Interest Paid | Remaining Balance |
|---|---|---|---|
| Year 1 | $4,373.62 | $1,496.23 | $20,626.38 |
| Year 2 | $4,666.53 | $1,203.32 | $15,959.86 |
| Year 3 | $4,979.05 | $890.79 | $10,980.81 |
| Year 4 | $5,312.51 | $557.34 | $5,668.30 |
| Year 5 | $5,668.30 | $201.55 | $0.00 |
This calculator models a standard fully amortizing fixed-rate loan, the kind used for most auto loans, personal loans, student loans, and fixed-rate mortgages. You pay the same amount every month, and each payment is split between interest (the cost of borrowing) and principal (the money you actually owe). Early in the loan, most of your payment goes toward interest because the balance is large. As the balance shrinks, more of each payment chips away at the principal. This shifting split is called amortization, and it is the reason a loan feels slow to pay down at first and then accelerates near the end.
You provide four inputs: the loan amount (the principal you borrow), the annual interest rate, the term in years, and an optional start date used to label the amortization schedule with calendar years. From those, the tool computes your fixed monthly payment, adds up every interest charge across the life of the loan, and reports the total cost — principal plus interest — so you can see exactly how much borrowing that money will cost you.
The monthly payment comes from the standard amortization formula:
Where M is the monthly payment, P is the principal (loan amount), r is the monthly interest rate (the annual rate divided by 12, then divided by 100 to convert from a percentage), and n is the total number of monthly payments (years × 12). When the interest rate is zero, the formula would divide by zero, so the calculator falls back to a simple P / n split in that case.
To build the schedule, the tool walks month by month. Each month it charges interest equal to the current balance times the monthly rate, subtracts the remaining part of the payment from the balance as principal, and carries the new balance forward. The final payment is capped so the balance lands exactly at zero rather than going slightly negative from rounding.
Suppose you finance a $25,000 car at a 6.5% annual rate over 5 years (60 months). The monthly rate is 0.065 / 12 ≈ 0.0054167. Plugging into the formula gives a monthly payment of about $489.15. Over 60 payments you pay roughly $29,349 in total, which means about $4,349 in intereston top of the $25,000 you borrowed. In the first month, interest is 25,000 × 0.0054167 ≈ $135.42 and the rest (about $353.73) reduces the principal. By the final year, almost the entire payment goes to principal.
Now consider a $10,000 personal loan at 11% over 3 years (36 months). The monthly rate is 0.11 / 12 ≈ 0.0091667, and the monthly payment works out to about $327.39. Total payments come to roughly $11,786, so you pay about $1,786 in interest. Personal loans usually carry higher rates than secured auto loans because there is no collateral backing them, which is why the interest share is larger relative to the amount borrowed even over a shorter term.
A useful takeaway from both examples: the two biggest levers on total interest are the rate and the term. A longer term lowers your monthly payment but increases total interest, because the balance stays high for longer. Shortening the term or making extra principal payments can save a surprising amount over the life of the loan.