The Loan Repayment Calculator shows exactly how a loan is repaid period by period, splitting each payment into the portion that covers interest and the portion that actually reduces the balance, all the way down to payoff. Enter the loan amount, the annual rate and the term, and the calculator returns the monthly payment along with a full repayment schedule tracking the balance to zero.
A single payment figure answers "how much do I owe each month," but it does not answer "how much of that payment is actually paying down what I borrowed." This calculator is built around that second question, making the repayment process itself, not just the payment amount, the primary focus.
*These results are estimates for information only, not lending advice.*
See the payment split into interest and principal
Every payment on an amortized loan is divided into two parts: interest, calculated on the remaining balance at the periodic rate, and principal, whatever remains of the payment after interest is covered. Interest for a period equals Remaining Balance x Periodic Rate; principal for the period equals Payment minus that period's interest.
Take a $20,000 loan at a 7% annual rate over 5 years (60 monthly payments), which carries a fixed monthly payment of approximately $396.02. In the very first month, the full $20,000 balance is still outstanding, so interest is 20,000 x (0.07/12), or about $116.67, meaning roughly $279.35 of that first payment actually reduces the principal. As the balance falls in later months, the interest portion shrinks and more of each identical $396.02 payment goes toward principal instead.
Track the balance falling to zero
The Loan Repayment Calculator's schedule follows the remaining balance from the full original loan amount down to exactly zero at the final payment, showing precisely how much is still owed after any given month along the way.
This running balance is useful for anyone who wants to know what payoff amount would be required at a specific point in the loan's life, not just at the very beginning or the very end.
By the time this $20,000, 7%, 5-year loan reaches its final months, the remaining balance is small enough that almost the entire $396.02 payment goes to principal, with only a small residual interest charge, a sharp contrast to the roughly 70/30 interest-to-principal split the very first payment carried.
Understand total interest across the full repayment
Adding up every period's interest charge across the entire schedule gives the total cost of borrowing beyond the original principal. On the $20,000, 7%, 5-year example, total interest across all 60 payments comes to approximately $3,761.48, meaning total payments made over the life of the loan sum to roughly $23,761.48 against the $20,000 originally borrowed.
Seeing that total broken down period by period, rather than as a single lump total interest figure, makes clear exactly when in the schedule most of that interest is actually charged: heavily weighted toward the early months, tapering steadily as the balance declines.
Use the schedule to plan extra payments
Because the Loan Repayment Calculator shows the exact remaining balance after any given payment, it is a useful reference point for estimating the effect of an extra principal payment made at a specific point in the schedule.
Paying down additional principal earlier in the loan, while the balance and therefore the interest charge is largest, removes more future interest than the same extra payment made later, once the balance has already shrunk considerably.
Comparing the standard schedule against a version with a lower starting balance (approximating an early extra payment) shows roughly how much interest such a payment could save.
Know what this schedule assumes
This calculation assumes every payment is made exactly on schedule for the full term, with no missed payments, no additional principal payments beyond the contracted amount, and no fees layered into the payment.
Real loans may allow extra payments, charge late fees for missed payments, or include escrow and insurance costs on top of principal and interest that this pure repayment schedule does not include.
Use the Loan Repayment Calculator to understand exactly how a standard loan pays down over time, and to estimate roughly how extra payments at different points in the schedule might shorten the payoff or reduce total interest.
Frequently asked questions
How is a loan payment split between interest and principal?
Each payment is split by first calculating interest as the remaining balance multiplied by the periodic interest rate, then assigning whatever is left of the fixed payment to principal. As the balance falls over time, the interest portion shrinks and the principal portion grows.
How much of the first payment on a $20,000, 7%, 5-year loan goes to interest?
On a $20,000 loan at 7% over 5 years, the first monthly payment of approximately $396.02 includes about $116.67 in interest and about $279.35 in principal, since the full loan balance is still outstanding at that point.
What is total interest on a $20,000 loan at 7% over 5 years?
Total interest on a $20,000 loan at a 7% annual rate over 5 years, repaid in 60 monthly payments, comes to approximately $3,761.48, making total payments over the loan's life about $23,761.48.
Why does the interest portion of each payment shrink over time?
The interest portion of each payment shrinks over time because interest is calculated on the remaining balance, which falls with every payment. As the balance gets smaller, the interest charge on that smaller balance also gets smaller, leaving more of each identical payment to reduce principal.
Can this calculator help estimate the effect of an extra payment?
Indirectly, yes. Comparing the standard schedule against one run with a lower starting balance approximates the effect of an early extra principal payment, showing roughly how much interest could be saved by paying down the balance sooner in the schedule.
Summary
The Loan Repayment Calculator tracks a loan's payoff period by period, splitting each payment into interest (Remaining Balance x Periodic Rate) and principal (the rest of the payment).
On a $20,000 loan at 7% over 5 years, the first payment of about $396.02 splits into roughly $116.67 interest and $279.35 principal, shifting steadily toward principal as the balance falls, with total interest over the term of about $3,761.48.
This period-by-period view supports planning extra payments and understanding true borrowing cost. Figures shown are estimates, not lending advice.