Interest Calculators

When a rentor leaves a property, they may be owed interest on their security deposit. Manually determining the interest can be tedious, and provides ample opportunity for error. Unfortunately, the steps to calculate this interest are not easily reproduced in spreadsheets such as 123 or Excel - the standard tools for accounting tasks.

We've taken the guesswork out of it for you! With the new Interest Calculator series, calculating interest owed is as simple as entering the move-in date, move-out date, and the amount of initial deposit.

Everything can be done with one hand. Use pull-down menus to enter the dates - this eliminates any problems caused by mistyped dates or incorrect date formats. Extra days for leapyears are automatically added, and the program's use of a four-digit year avoids the Y2K "bug".

The deposit amount is similarly entered using the mouse and an on-screen keypad. (the option to use the keypad on the keyboard is planned for future versions of the program)

Once you click that last digit, the program will kick into gear and calculate the interest owed. Results are presented in an easy to read form so you can confirm the data before writing the check.

(image reduced from actual size)

You won't find an easier program - even "computer challenged" people will be able to use it with little or no instruction. And to top it off, this program is FREE. You can install it on as many computers as you'd like, and share it with others (as long as you don't modify the files, or charge a fee for the program).

  Virginia
NOTE! It is with deep regret that I must discontinue support for the Virginia Interest Calculator at the end of 2010. It's possible that I may find the time to pick it up again in the future, so please email me if you'd like to be added to my contact list. (your email address will not be distributed to anyone else, or used by me for any other reason than to contact you regarding this program)


In Virginia, interest is owed when a rentor has been on the property for 13 months or longer. This simple interest is calculated daily based on a rate that varies from year to year (one percent below the federal Discount loan rate as of the first of the given year - to a minimum of zero percent).

The images above were taken from the Virginia Interest Calculator. Note that the program itself will not determine whether whether the 13-month requirement has been met, and will allow time periods of less than 13 months to be entered. It is up to the user to determine whether the rentor has stayed on the property long enough to warrant interest.

To upgrade to a newer version of a program, simply install the new version into the same directory as the older version. The program (starting with version 2004.01.00) has the ability to update the loan rates that it uses automatically.

Click here to download the latest version (v2008.09.12) - 2.6M

Data Updates: The program is able to automatically update itself with new data when it is available - all that is needed is an internet connection. If you have problems updating the data automatically, there is a manual method provided. First, download this file and save it to your hard drive - do not open, edit, or rename the file:

virginia interest calculator data.zip

Then in the calculator program, click on the Update button on the main page, and the Manual Update button on the Updates page. You'll be given an "open" dialog - use it to select the file you just downloaded and click OK. If you don't receive a "successfully updated" message, make sure that the filename appears exactly as it does in the above link and try again.

  New Jersey

In New Jersey, the amount of interest owed depends on the actual interest the deposit monies accrue in the landlord's bank. The New Jersey Interest Calculator allows landlords and property managers to enter different interest rates for each month.

Click here to download the latest version (v2004.01.00) - 1.6M