Loan setup form
Enter core loan details, choose a payment pattern, and test extra payments to see how principal and interest shift over time.
Example data table
This sample shows how a repayment plan can be reviewed before entering your own numbers.
| Input or Output | Example Value | Why it matters |
|---|---|---|
| Loan amount | $180,000.00 | Sets the principal balance that must be repaid. |
| Annual interest rate | 5.80% | Controls how much interest is charged each period. |
| Term | 20 years | Defines the planned repayment window. |
| Payment frequency | Monthly | Changes the number of payments per year. |
| Recurring extra payment | $150.00 | Reduces principal faster and lowers total interest. |
| Estimated regular payment | $1,268.83 | Shows the planned installment before extras. |
Formula used
Periodic rate: r = annual interest rate / payments per year
Use the annual rate as a decimal before dividing by the payment frequency.
Regular payment: Payment = P × r / (1 − (1 + r)−n)
Here, P is loan amount, r is periodic rate, and n is total payments.
Interest for a period: Interest = beginning balance × r
Each payment first covers interest, then reduces principal.
Ending balance: Ending balance = beginning balance − principal paid − extra payment
Extra payments shorten the loan when applied directly to principal.
How to use this calculator
- Enter the original loan amount and annual interest rate.
- Choose the term in years and any extra months.
- Select monthly, biweekly, weekly, or quarterly payments.
- Set the first payment date so the schedule aligns with your plan.
- Add recurring or one-time extra payments if you want faster payoff.
- Click calculate to show the summary, chart, and full schedule above the form.
- Download the current table as CSV or PDF for reporting or sharing.
Frequently asked questions
1. What does this calculator show?
It shows each payment date, beginning balance, scheduled payment, principal, interest, extra payment, and ending balance. It also summarizes total interest, total paid, and expected payoff date.
2. Why does interest start high and later decline?
Interest is calculated on the remaining balance. Early in the loan, the balance is highest, so interest is larger. As principal declines, each new period generates less interest.
3. How do extra payments affect the schedule?
Extra payments go directly toward principal. That lowers future interest charges, reduces the remaining balance faster, and often shortens the total number of payments needed.
4. Can I use weekly or biweekly payments?
Yes. The calculator supports weekly, biweekly, monthly, and quarterly payment frequencies. The periodic rate and total number of payments adjust to match your selected repayment pattern.
5. What happens when the interest rate is zero?
When the rate is zero, the payment is simply the loan amount divided by the number of payments. Every payment reduces principal because there is no interest charge.
6. Why is the final payment sometimes different?
The last payment may be smaller because only the remaining balance and final interest are due. Extra payments and rounding can also change the final installment amount.
7. Should I round each period?
Rounding each period makes the schedule feel closer to many lender statements. Leaving it unchecked keeps more mathematical precision throughout the full amortization calculation.
8. Can I export the schedule?
Yes. After calculating, you can download the current schedule as a CSV file or a PDF file. That helps with recordkeeping, comparisons, and discussions with lenders.