Calculator Inputs
Example Data Table
This sample shows how a daily simple interest loan can be entered.
| Loan Amount | APR | Start Date | First Payment | Frequency | Payments | Extra Payment |
|---|---|---|---|---|---|---|
| $25,000 | 8.50% | 2026-04-26 | 2026-05-26 | Monthly | 60 | $50 |
| $12,500 | 10.25% | 2026-04-26 | 2026-05-10 | Biweekly | 80 | $25 |
| $40,000 | 7.75% | 2026-04-26 | 2026-06-01 | Monthly | 72 | $100 |
Formula Used
Daily interest rate: Annual rate ÷ day count basis.
Interest for period: Beginning balance × daily rate × days between payments.
Interest paid: The payment first pays current and unpaid interest.
Principal paid: Payment − interest paid.
Ending balance: Beginning balance − principal paid.
Total interest: Sum of all interest paid rows.
When the scheduled payment is zero, the tool estimates a level payment. It uses the average days in the chosen payment frequency. The final daily schedule may still adjust the last payment.
How to Use This Calculator
- Enter the loan amount and annual interest rate.
- Select a 365-day or 360-day interest basis.
- Add the loan start date and first payment date.
- Choose the payment frequency.
- Enter a scheduled payment, or enter zero for an estimate.
- Add recurring or one-time extra payments if needed.
- Press the calculate button.
- Review the results, chart, and amortization table.
- Download the CSV or PDF report for records.
Why Daily Simple Interest Matters
Daily simple interest changes with time. Each day adds interest to the unpaid principal. This matters when payments arrive early or late. A monthly calculator may hide that effect. A daily schedule shows each date. It also shows how much interest built up before a payment.
Better Planning for Real Loans
Many personal loans, auto loans, equipment notes, and private finance agreements use daily accrual. The payment first clears earned interest. The remaining amount reduces principal. When the payment is small, principal falls slowly. When extra money is added, the balance drops faster. This calculator helps you test those choices before you commit.
What the Schedule Shows
The table breaks every payment into useful parts. You can see days in the period, interest charged, principal paid, extra amount, remaining balance, and cumulative interest. The chart gives a faster view. It shows whether the balance is falling smoothly. It also highlights periods where interest consumes too much of the payment.
Using Extra Payments Wisely
Extra payments can shorten the payoff date. They also reduce total interest because future interest is based on a smaller balance. Even a small recurring extra amount can create a clear saving. A one-time extra payment can be tested on any date. This is useful for bonuses, refunds, seasonal income, or project cash flow.
Important Limits
The calculator uses a practical daily simple interest model. It does not replace lender disclosures. Some lenders use fees, late charges, minimum interest rules, or special rounding policies. Some agreements also treat missed payments differently. Always compare the result with your contract. Still, this tool is useful for estimates, planning, and scenario review.
Best Use Cases
Use it when you need a transparent daily amortization schedule. It works well for planning early payoff, comparing payment frequencies, checking extra payments, and understanding interest timing. Export the CSV for spreadsheet review. Use the report button when you need a clean summary for records or client discussion. Keep the starting date accurate. A wrong date changes daily interest. Review the first payment date carefully. It controls the first interest period and can affect every later balance in the schedule.
FAQs
1. What is daily simple interest?
Daily simple interest means interest accrues each day on the unpaid principal. It does not compound daily in this model. The payment usually covers interest first, then reduces principal.
2. Why does the first payment date matter?
The first payment date sets the first interest period. A longer first period creates more interest. A shorter first period creates less interest before the first payment.
3. What happens when I enter zero as payment?
The calculator estimates a level payment using the loan amount, rate, frequency, and number of payments. The actual daily schedule then applies exact day counts.
4. Does an extra payment reduce interest?
Yes. Extra principal lowers the balance. Future daily interest is based on that lower balance. This can reduce total interest and shorten payoff time.
5. What is a 360-day basis?
A 360-day basis divides the annual rate by 360. Some finance contracts use it. It usually creates slightly higher daily interest than a 365-day basis.
6. Why is unpaid interest shown?
Unpaid interest appears when a payment is not large enough to cover accrued interest. This warning helps identify possible negative amortization risk.
7. Can I use this for auto loans?
Yes, if the loan uses daily simple interest. Many auto loans use daily accrual. Check your lender agreement for fees, rounding, and payoff rules.
8. Is the exported report final lender data?
No. The report is an estimate based on the inputs. Lenders may apply fees, posting delays, rounding rules, or other contract terms.