July 2020: Major Update: Ultimate Financial Calculator    3 New Calculators: Refinance Calculator, Lease vs. Buy Calculator & Break-Even Calculator
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This compound interest calculator calculates interest between any two dates. A dozen compounding frequencies are supported (did we miss any? :). You can also enter negative interest rates.

Because this calculator is date sensitive, and because it supports many compounding options, it is a suitable tool for calculating the compound interest owed on a debt. You can use it to calculate accrued interest from a point in time when the balance is known. Because this calculator allows for odd days (example three months plus five days), you may calculate interest due for any investment or debt. More details below the calculator


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Compound Interest

Compound interest means that interest gets paid (or is earned) on previously unpaid interest.

For example, if the interest rate is 2% and you start with $1,000 after the end of a year, you'll earn or owe $20 in interest (using annual compounding). Then at the end of two years, assuming there have been no withdrawals (or payments) you earn $20.40, not $20. The previous period's interest earned interest as well.

This pattern is called compounding, and it repeats as long as the money stays invested, or the debtor owes on the debt.

If you are an investor, you want to compound interest. If you are a debtor, you want to avoid it, particularly if you ever miss a payment or a payment is not enough to cover the interest due.

You can use this online interest calculator as a:

  • apy calculator
  • daily interest calculator
  • investment interest calculator
  • loan interest calculator
  • negative interest rate calculator
  • savings interest calculator

As a side benefit to this calculator's date accuracy, you can use it for date math calculations. That is, given two dates, it will calculate the number of days between them, or it will find the date that is "X" days from the first date.

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41 Comments on “Compound Interest Calculator”

financial online calculator Join the conversation. Tell me what you think.
  • Does the ‘Interest Earned’ calculation use rounding?

    I was trying an exercise creating an Excel spreadsheet. I used your financial calculator as a comparison using the following variables:
    -entered start date 15 May 2018
    -entered end date 15 May 2019
    -‘365 days calculated’
    -entered PV of $1500
    -entered Annual Interest Rate 15%, (but I used your daily calculation of 0.0411%.)

    Your calculator said $225 Interest Earned, but my spreadsheet calculated $225.02

    Thanks for your help.

    • All calculators that display a float, will round. So yes, this calculator rounds.

      But the calculated interest is accurate to the penny. It just so happens that the interest for the year is an even $225.

      So, what’s going on? The rounding is happening where you aren’t expecting it. The daily interest rate is not actually 0.0411%.

      I did not realize the someone might want to use the daily interest rate shown here for calculating purposes. The next time I make a change to this page, I’ll look into increasing the number of digits shown for the daily rate so that user’s hand calculations can be accurate to the penny too!

      • Hello Karl. Am dealing with shortages on invoicing…and calculating compounded interest with additions every couple of months. Here are the numbers and dates. Please let me know how this is worked out…
        Jan 10/2019 419.86
        March 10/2019 322.02
        April 10/2019 407.12
        June 10/2019 663.12
        Aug 10/2019 12936.00
        Oct 10/2019 21695.70
        Jan 10/2020 27984.22
        Feb 10/2020 16744.68
        June 10/2020 8896.72

        • Hi Dale. I’m not sure I completely understand your question. Taking the first example, are you saying there was an invoice due on Jan 10, 2019, for $419.86 and it has not been paid and you want to add interest to the balance? If so, plug in the amount and for the first date enter Jan 10, 2019, and for the 2nd date enter today. Pick your compounding and interest rate and calculate and add the interest to the amount of the invoice. If there is more to it than this, let me know.

          • Thanks Karl. The problem is adding each shortage to the equation. After the 1st entry, there is no option to add the next. And the next. All entrys have the same end date…but each new entry raises the total amount to be processed.

          • I see. Right, this calculator, as you have discovered, is for calculating interest for one amount.

            Those amounts, are they invoice balances as of the dates indicated without any interest accruals?

            You have two options that I can think of right now:

            1. Calculate the interest for each amount and term individually and then add up the interest amounts.
            2. Use this calculator. Set the cash flow type to either invest or savings. Scroll down the page to the tutorial and check out the first one for an overview and the one on future value. The calculator will do the calculation, but the labels may not be what you would normally expect. The Windows program C-Value! is the same calculator. It will let you change the label descriptions i.e. "Buy" or "Sell"
  • There are default START & END date YEAR errors. Default start used to be current mo/day/yr with default end date 1 year later.
    Current START DATE defaults to 2018 vs 2019 & END DATE defaults to current mo/day/yr vs 2020.
    Can you please fix this?

    • I understand, and I though that was the way it did work, but I went back to a version from August 2017, and it used the same defaults as today.

      The thinking is, if I owe interest or I am owed interest as of today, what is the amount owed? To answer that question, all one has to do is to set the first date.

      But you obviously are doing forward looking calculations, which means you need to reset both dates. If I change it though, someone else isn’t going to be happy. I will look at seeing if I can add a "Today" option on the calendar so that all a user need to is click once to set to current date.

    • I’ve been trying to use your OL calculator today but now it no longer appears on your website. Only the comments are displayed?? Help??!!

        • Hello, financial-calculators.com is back up and running. I’m sorry for the problems you experienced. An automatically applied update went wrong and it eventually brought down the entier site on Tuesday. Unfortunately, I could not figure out the problem and get it fixed until late Tuesday (eastern time USA). Thank you for reporting the problem.

      • Hello, financial-calculators.com is back up and running. I’m sorry for the problems you experienced. An automatically applied update went wrong and it eventually brought down the entier site on Tuesday. Unfortunately, I could not figure out the problem and get it fixed until late Tuesday (eastern time USA). Thank you for reporting the problem.

  • There are no financial calculators available
    Error message: Financial Calculators – These calculators are not toys.

    • Hello, financial-calculators.com is back up and running. I’m sorry for the problems you experienced. An automatically applied update went wrong and it eventually brought down the entier site on Tuesday. Unfortunately, I could not figure out the problem and get it fixed until late Tuesday (eastern time USA). Thank you for reporting the problem.

  • Your online calculators have been very useful for me, including the nicely formatted print options. I would like to suggest/request that the print format for the compound interest calculator print the website address and the date and time printed.

    At least one of the other calculators on your website, the loan amortization schedule, includes that information when printing. I believe the print function for the loan amortization schedule uses the default header and footer options of the web browser. For instance, I’m using Firefox on Windows, and my page setup options include the website address on the upper right, the date and time in the lower right, and the page number in the lower left; and when I’ve used the print button on the loan amortization calculator, I get those same headers and footers.

    It would be great if the compound interest calculator could do the same thing. As it is, when I print (or print to a PDF), there are no headers or footers. What is most important to me is having it be clear to me (or others) the website that produced the calculation.

    Thanks again for making these available.

    • Thanks for your suggestion Rob. I had always thought that businesses would rather not have a source on the printout. I’ll have to think about it. Further, the reason why the calculators do not have it and the schedules do have the information, is because different techniques need to be used to handle the printing. The name on the schedule is a byproduct of the technique, it’s not something I specifically added (or I don’t recall adding it 🙂 ).

  • If a CD interest is compounded annually from June 2019 to June 2020, have I been getting CD interest in 2019? Will I get 1099-INT for the year 2019?

    • Hi John, First, I’m not an accountant or a tax professional. I can only say about the word "get." You should be able to answer that. If you have access to the interest, that is, if you can withdrawal it (or will be able to do so before 12/31/2019), spend it or reinvest is, then you got it or will get it. However, what i "think" is the case is, the interest will be "accruing", that is, owed to you, but you’ll have no access to it. And if that’s the case, then I don’t think a 1099-INT will be issued. BUT, an that’s a big BUT, this may vary due to jurisdiction or to the exact terms of the CD you reference. So absolutely no tax advise is being offered here.

  • Hi Karl,

    Thank you for your amazing calculator. I was using the simple interest calculator for my business for about a year and now I am using the compound interest one.

    I noticed that the APY for daily compounded is lower than the APY for monthly compounded interest. Correct me if I am wrong but I think daily APY’s are usually higher than monthly.

    Looking forward to your reply.

    Thanks.

    • Thanks Rikhil. I’m happy to hear that the calculators have been useful for you.

      To your specific question, that’s not always the case. For example, if you reload the page and use the calculator default values, the APY with daily compounding is higher than for monthly compounding.

      I would need to know your specifics before I can provide more details, but I assume it has to do with odd days or fractional periods.

      If you want to take this further, without getting into the equation details, include the custom URL from the box below the calculator for each calculation in any follow-up you might have.

      • My data is as follows:

        Amount: $6,477,529.68
        Annual Interest Rate: 16.284%
        Days: 30
        Start Date: 06/28/2019
        End Date: 07/28/2019
        Compounding: Daily
        Days in Year: 365

        I get an APR of 17.6806% for daily compounded and an APR of 17.8204% for monthly compounded.

        • The APY is higher with monthly compounding for the short duration of 30 day because monthly compounding earns more interest than daily compounding earns.

          Change the days per year to 360, and that will no longer be the case.

          Or extend the term slightly to 60 days (end date August 28th) and days per year left at 365 and daily compounding results in more interest (and higher APY).

          (Give the custom URL feature a try. It saves everyone from retyping the inputs.)

  • Annual Interest rate (%) given by Bank 0.08250 = 8.250%
    Number of Period (months*years) 365
    Monthly Interest Rate (%) per month 0.0002 = 0.02260%
    Deposited Amount $5,000,000.00
    Per Day interest achieved $113.01
    Calculation of Amount Received based on Interest Per Month $3,503.42

    Can you help me with the formula please as your result generate the correct values but my sheet is not generating it.
    Ref to (amount Received based on Interest Per Month vs Interest Earned)

    Starting Amount = $500,000
    Annual Interest Rate = 8.25%
    Days = 365
    Interest Earned = $41,250
    Daily interest Rate = 0.0226%

    • I can answer two type of questions, what calculator do I use, and how do I use a calculator or feature?

      I can’t get into answering questions about the formulas, because that gets into the weeds too much — where one question leads to another, and I need to create new calculators, content and support the users. I can say this, that the programming code for the equation for this calculator is a couple hundred lines long.

  • Pesky Pattie says:

    I cant seem to find a calculator that uses APY, NOT APR, to calculate how much interest would be earned on a specific amount of money for a specific amount of time. Most rates are being reported in APY, which ALREADY takes into account how the interest is compounded, so there is no need to have to select “how compounded”. However, most of the calculators Im finding either ask for APRate & how compounded, which I don’t need since most are quoted in APY. OR, most of the calculators ask for APY (YIELD) & ALSO ASK for HOW COMPOUNDED, which does NOT give a correct result for interest earned, since APY ALREADY takes “how compounded” into consideration. The calculator should either ask APR (Rate) AND How Compounded, OR JUST ASK APY. Does anyone know where we can find a calculator that correctly just asks for APY, and then of course; amount of $, any $ added on regular basis or not, & earning for how long?

    • The APY is a yield, not an interest rate, and the formula for calculating interest uses rate, not yield.

      Can you back into the compounding by performing a few test calculations?

  • I found an error when I calculate interest earned for a month compounding annually. In this case the calculator shows APY as 12,68% which is obviously incorrect since with annual compounding it should be 12%

    • You didn’t mention what annual interest rate you used. But, APY is a yield, not an interest rate. The equation used, is provided by the US Gov’t in the Truth-in-Saving Act and not something I just came up with. The calculator has proven to be correct for all test cases when compared with the examples in the regulation.

      • Thanks, Karl.
        The annual interest rate I used was 12% compounding annualy. I rely only on simple math and not on any “Acts”. APY of 12,68% is a en error since there is no compounding during one year.

        • I see. Than all I can say Sergey, is the calculation may not be what you want, need or expect, but it is not wrong.

          Here’s the Truth-in-Savings Act equation for APY

          US Law requires all depository institutions to provide depositors with the APY calculated as specified. This allows US consumers to compare results offered by banks and other depository institutions.

          In your case, the reason why the yield is greater than 12% is because you are telling the calculator that the funds are deposited for only 30 or 31 days and you want your interest. You can then take the principal and interest and reinvest it (in effect compounding your return) and that’s why the YIELD is greater than the 12% interest RATE.

          If you redo the calculation for 365 days, and used a 12% rate with annual compounding then the APY will be 12%.

  • Hi,

    I need your help.

    I changed the currency and date format but I could not find “save changes” button.

    Can you please help me educate on this?

    Thank you Sir.

    Sincere Regards
    Micheal

    • Hello, my guess is, you are using a mobile device, right? If so, the change currency window might be too large. When you open the currency change window, try holding the device vertically so that you can see the bottom of that window. Let me know if that works, please.

      I’ll work on making a better layout.

      • Hello Karl,

        I am using W10 PC. I think I had not scroll further down whereby as I was not able to view because of the size of window.

        It is perfectly fine now and I am able to save and set the currency and date format as I want.

        Thank you for your help.

        Sincere Regards
        Micheal

  • If we’re trying to calculate compound interest for a partial year what should the formula be? For example, if we assume we invested $100 at a 7% rate compounded annually for 100 days, should the formula be Interest = 100*(1.07)*100/365? Or should it be Interest = 100*(1.07)^100/365? The calculator seems to be using the former which provides an Annual Percentage Yield of greater than 7%.

    Thanks in advance!

    • Hi Emily, there are two types of questions I’m able to answer on this site. What calculator should I use to accomplish "X." And how do I use a calculator’s feature? I don’t have the equations in my head and if I started to research them again, I would spend more time doing that than building the site.

Comments, suggestions & questions welcomed...

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