Daily Compounding Or Simple Interest Calculator: Calculate Interest Between Dates Or For A Specified Number Of Days

Daily Interest Calculator Sign

This Daily Interest Loan Calculator will help you to quickly calculate either simple or compounding interest for a specified period of time.

You can either calculate daily interest for a single loan period, or create a loan schedule made up of multiple periods, each with their own time-frames, principal adjustments, and interest rates.

Plus, you can print out a copy of the running balance schedule so you can just start from where you left off on your next visit.

All these features make the calculator ideal for tracking personal loan interest, promissory note interest, or other types of owner-financed, interest-bearing notes.

And finally, in case you're wondering how this calculator came into being, it was born out of the following email I received:

I need a simple interest, daily accumulated interest to do a running balance due including the principal. Spreadsheet?

Example, I loan a customer $13,000.00 on a note, 10% annual (360 days) simple interest. The loan is usually secured, sometimes not. Generally, these are 6-month notes, but due dates are not important. No regular payments, monthly or otherwise.

Here is what and where I need help on.

At some point in time, my borrower may send me a payment of $9,050.00 which is applied to the note and then two months later borrows $2,750.00, increasing the note. Then the next month, the borrower sends me $500.00 for the next three months running to be applied to the note.

I love getting those kinds of emails! They get my wheels turning and allow me to serve others through a work I love.

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Daily Interest Calculator

Calculate daily interest between dates or number of days, simple or compounding, and for one or multiple periods.

Special Instructions

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Selected Data Record:

A Data Record is a set of calculator entries that are stored in your web browser's Local Storage. If a Data Record is currently selected in the "Data" tab, this line will list the name you gave to that data record. If no data record is selected, or you have no entries stored for this calculator, the line will display "None".

DataData recordData recordSelected data record: None
Loan Start & PrefsLoan Start and PrefsLoan Start Values and PrefsLoan Start Values and Preferences

Loan Start Values and Preferences:

Note that you can change these starting variables and preferences at any time, as the changes will automatically recalculate the loan schedule.

Name:Name:Loan name:Loan name:

Loan name:

Optional: Enter the name of the loan as you'd like it to appear on the printed loan periods report.

Start Amt:Start amt:Starting amount:Starting amount:

Starting amount:

Enter the beginning loan amount, without the dollar sign or any comma.

Rate:Interest rate:Annual interest rate:Annual interest rate:

Starting annual interest rate:

Enter the starting annual interest rate expressed as a percentage, but without the percent sign (for 6.5%, enter 6.5).

Start date:

Start date:

Select the month and day, and enter the 4-digit year of the date this loan will start accruing interest charges.

Method:Int method:Interest method:Daily interest method:

Daily interest method:

Select either Simple Interest or Compounding Interest. Simple Interest will not add period interest to the principal, whereas Compounding Interest will add the daily interest charge to the principal on a daily and period basis.

Days/year:Days in year:Days in year:Days in year:

Days in year:

Select the number of days per year you would like the calculator to use for converting the annual interest rate to a daily interest rate.

Period Interest CalculatorPeriod Interest CalculatorPeriod Interest CalculatorPeriod Interest Calculator

Period Interest Calculator:

To calculate the interest for the period, be sure you have entered the starting amount, rate, and date (including the 4-digit year) in the top section, then complete the required fields (ending 4-digit year and number of days in period) in this section, then click the Calculate Daily Interest button.

If you will be entering more than one interest period, be sure to enter all periods in the order they occurred, from first to last.

Optional principal adjustment:

If the borrower made a payment on the loan, select Decrease from the dropdown menu and enter the amount of the payment. If you loaned the borrower additional funds or you need to assess a late penalty, select Increase from the dropdown menu and enter the amount to increase the principal by. Otherwise, if no loan adjustments occurred in the period, leave the field blank.

End date:

Period end date:

Select the month and day, and enter the 4-digit year of the date this loan period ended.

# days:# of days:Number of days:Number of days in perod:

Number of days in period:

If you entered a date in the previous line, the number of days in this interest period will be calculated for you. Otherwise, you can enter a number of days in this field and the calculator will update the month, day, and year in the previous line for you.

New rate:New rate:Period rate:Period rate (if different from start rate):

Period rate (if different from start rate):

If the rate charged for this interest period is different from the starting rate, enter the new rate on this line, but without the percent sign (for 6.5%, enter 6.5). Otherwise, if you leave the field blank, the calculator will use the starting rate for this period.

Interest:Period interest:Period interest:Period interest:

Period interest:

This is the amount of the interest that has accrued between the starting date (or the last entered period date) and the ending date of this period.

Period P&I:Period P&I:Period ending P&I balance:Period principal & interest ending balance:

Period principal & interest ending balance:

This is the loan payoff amount (principal plus accrued interest) as of the ending date of this period.

Daily rate:

Daily rate:

This is the daily interest rate being applied for this period.

If you would like to save the current entries to the secure online database, tap or click on the Data tab, select "New Data Record", give the data record a name, then tap or click the Save button. To save changes to previously saved entries, simply tap the Save button. Please select and "Clear" any data records you no longer need.

Help and Tools


How to Calculate Daily Interest

Now, if you're like me, and need to know what's going on "under the hood", here is how I set up the calculator to calculate daily interest.

How To Calculate Daily Interest

To illustrate how to calculate daily interest, I'll use the following example:

  • Original principal: $10,000
  • Annual Interest Rate: 10%
  • Number of days: 90
Simple Daily Interest

To calculate the daily simple interest on a $10,000, 10% note for 90 days (please allow for rounding differences):

  1. Convert the percentage rate to a decimal: 10 ÷ 100 = 0.10
  2. Convert the annual rate to a daily rate: 0.10 ÷ 365 = 0.00027397
  3. Multiply the daily rate by the principal: 10000 × 0.00027397 = $2.74
  4. Multiply the daily interest by the number of days: $2.74 × 90 = $246.60

Since we're calculating simple interest, the $246.60 is not added to the principle for any subsequent periods.

Compounding Daily Interest

To calculate the daily compounding interest on a $10,000, 10% note for 90 days (please allow for rounding differences):

  1. Convert the percentage rate to a decimal: 10 ÷ 100 = 0.10
  2. Convert the annual rate to a daily rate: 0.10 ÷ 365 = 0.00027397
  3. Add 1 to the daily rate: 1 + 0.00027397 = 1.00027397
  4. Raise the daily rate factor to the number of days: 1.0002739790 = 1.0249538
  5. Subtract 1 from the raised factor: 1.0249538 - 1 = 0.0249538
  6. Multiply the principal by the 90-day rate factor: 10000 × 0.0249538 = $249.54

Since we're calculating compound interest, the $249.54 is added to the principal for the next compounding period.

Adjust Calculator Width:

Move the slider to left and right to adjust the calculator width. Note that the Help and Tools panel will be hidden when the calculator is too wide to fit both on the screen. Moving the slider to the left will bring the instructions and tools panel back into view.

Also note that some calculators will reformat to accommodate the screen size as you make the calculator wider or narrower. If the calculator is narrow, columns of entry rows will be converted to a vertical entry form, whereas a wider calculator will display columns of entry rows, and the entry fields will be smaller in size ... since they will not need to be "thumb friendly".

Show/Hide Popup Keypads:

Select Show or Hide to show or hide the popup keypad icons located next to numeric entry fields. These are generally only needed for mobile devices that don't have decimal points in their numeric keypads. So if you are on a desktop, you may find the calculator to be more user-friendly and less cluttered without them.

Stick/Unstick Tools:

Select Stick or Unstick to stick or unstick the help and tools panel. Selecting "Stick" will keep the panel in view while scrolling the calculator vertically. If you find that annoying, select "Unstick" to keep the panel in a stationary position.

If the tools panel becomes "Unstuck" on its own, try clicking "Unstick" and then "Stick" to re-stick the panel.