Interest Tool

Daily Interest Calculator Tool

I wrote an Interest Calculation Tool (Windows 8/10 only) to assist a user to calculate Loans and the various other things needs at times when dealing with loans. This uses standard United States financial calculations. Some parts of the tool are still in progress.

DISCLAIMER: Absolutely No Warranty is given on this software as to the merchantability or fitness for a particular purpose. This is not a certified program, it is used for estimates only, and the calculations may not be used to create legally binding contracts.

My goal is to move the code to a Website and a PWA App, and an Android App.

If you would like to use a 30 Day Trial Version of the software, go to : http://bettencourtt.com/dailyint/publish.htm and install it from there.

Screenshots and Explanations:

Main Screen. Calculates Loans and full amortization with either Simple or Precomputed Rule of 78’s interest collection.

Calculates fixed term or fixed payment amount.

Calculates Daily Interest amounts, accrued interest between two dates, and even the number of periods between the dates.

New function coming soon is TDE (True Daily Earnings) Calculations.

Output the Amortization Table to an Excel Spreadsheet.

Loan Comparison. This screen shows the differences between two loans.

Calculate the Rule of 78’s Rebate of Finance Charges on a Precomputed Loan, with Optional Florida Acquisition Fee.



Solver Tools.
1. Given an accrued interest value, the program can estimate one of the three parameters:
— APR, Principal, or Days, as long as two of the three are known.
2. APR Estimation. Given the Principal, Actual Payment, and Number of Periods, the program estimates the original APR used to calculate the loan.
3. Given an Add-On rate, the program will calculate the Actual APR and terms for the loan.
4. Using the desired Payment, Down Payment, APR, and term, the program will calculate the Amount to Finance needed to arrive at the proposed loan.
5. Range calculation: Given a number to start with, the program will recalculate various loans with the same Payment and APR. See below:

Lease Calculations screen. This is for typical Automotive Leases.
Special Target Payment feature allows the user to enter a fixed payment amount, and choose to adjust the Money Factor, Residual, or Lease Price to arrive at that exact payment.

Given a Lease and a Loan calculation or roughly the same parameters, shows the differences between the two options.


I have not yet decided on a selling price. Sometime in the first quarter of 2021, I will put that information out there.