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This simple interest calculator calculates interest between any two dates. Per simple interest is "interest payable only on the principal." Interest is never earned or collected on previous interest.

Because this calculator is date sensitive, it is a suitable tool for calculating simple interest owed on any debt. You can calculate the accrued interest from any point in time when the balance is known. More details below the calculator



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Simple Interest

Simple interest is the interest calculation method that is least beneficial to savers and the most beneficial to borrowers.

But note, if payments on a debt are paid as frequently as the compounding and the payment covers the interest due, then even if the terms of the loan call for compounding, there will be no impact on the total amount paid because at no point will there be any unpaid interest.

When the terms of a debt call for a simple interest calculation, if a payment does not cover the interest due, the unpaid interest must be tracked separately from the unpaid principal balance (also known as the US Rule). We believe that our Time Value of Money Calculator is the only online financial calculator that gives users this option and creates a schedule that shows the unpaid interest balance.


103 Comments on “Simple Interest Calculator”

financial online calculator Join the conversation. Tell me what you think.
  • I found this today through need and it did exactly what I wanted it to do. It was very easy to work out and use. Good work.

  • Bank staff wouldn’t tell me how to compare income from higher-rate fixed term deposit (of say $2000) with income from lower compounding rate in online account. Eventually compounded income has to catch up – but in 3 or 30 years? Makes it hard to decide which a/c to put your money in.
    Haven’t tried a test run on your website yet.

  • Do you have or know of a calculator I can use to calculate simple/balloon interest for multiple loan amounts with the same interest rate that are all invested into the same investment on multiple dates but all get paid off on the same single date? I am a builder and we often borrow money from private investors for the same project. For example, Investor Karl gives me $300k on 2/1/2016 to purchase the investment property/house & to have some initial working capital. When the $300k is all used up, I borrow another $100k from Investor Karl on 6/15/2016. When that is used up, I borrow another $100k from Investor Karl on 12/1/2016. I need just $50k more to finish up renovating or building the home, so I borrow $50k more from Investor Karl on 2/1/2017. ALL of the loans are at a standard 8% interest rate with a balloon interest payment & all principle paid back at the same time upon closing the sale of the subject renovated or new home, which let’s say is happening tomorrow, 4/1/2017. I owe Karl a check for $550k to return all loans immediately after closing on 4/1/2017. To figure out the check I owe Karl for interest on his multiple loan amounts starting on multiple dates I enter into your simple interest calculator each start date (which varies), each loan amount (which varies), and the interest rate (which remains the same– 8% in this case) & end date (which remains the same– 4/1/2017 in this case) 4 separate times to calculate the interest on the 4 loans and then I write them down and add them up. This example is pretty easy, but on projects where I may have 18 different loan amounts on 18 different dates it gets time consuming to do 18 different interest calculations and add them all up in the end for a final total interest figure. If you had a calculator that would allow a borrower or investor to calculate total simple interest owed on multiple loan amounts on varying dates over time to be paid back all on the same day (upon a closing), that would be sweet!

    • Hi Jon, this calculation can easily be done by the Ultimate Financial Calculator on this site. Scroll down the page and there is a list of financial calculations. Check them out. Everyone should look at #1 to get an overview of how the calculator works. Then you’ll be most interested in:

      11. Construction Loan
      Generally a short term loan with multiple borrows

      And I’m not sure from your example, if you’ll need this one or not. You might if you make periodic interest only payments.

      14. Interest Only Loan
      Initial series of interest only payments

      Basically what you’ll be doing is entering the "investment" you mention as "loans". The final line will be an "Unknown" payment amount on the date you expect to pay it back. The calculator will calculate accrued interest and principal due.

      Please let me know how this works for you.

    • SoniA shields says:


      This calculation has saved me so many times
      From having a nervous breakdown when I have to do interest once a month. I would not hesitate to recommend it to anyone. Thank you for making it simple. This is a blessing from God

  • Please consider an update to the functionality of the date ranges. If I have to change just the month, I have to delete the whole thing. I wish I could just click and change specifically what I want. Also, remove the requirement to add a 0 before a month (05/01/2017). Other programs I use requiring me to enter a date range are more user friendly. This one has a learning curve for me and I do use it often for me job.

    Thank you for your consideration.

    • Hi JT, sorry not to reply yesterday. Time just got away from me.

      No doubt about it, date entry has caused users (and me) more headaches than anything else on this site. I am a bit confused as to how you are entering or changing dates. Do you want to type a date or do you want to use the pop-up calendar?

      If you want to type dates, do not try to edit them. When you tab to a date input, the date will be selected. Though it would seem to be faster to edit a date, in fact, typing 8 numbers is faster than trying to use a cursor key (which are blocked) and moving the input point a couple of digits, then use delete or backspace and then finally typing a month. (Or alternatively, taking your hand off the keyboard and using the mouse to click on the month part say and then edit it).

      So, if typing, and if you’re in the US, just tab to a date, and type:


      for today. Don’t type the date part separators even.

      If you want to change the date with the mouse, click on the calendar. If you want to change the month only, after the calendar opens, click in the top center on the current month and the calendar changes to month display. Select the month. Click the date again and the calendar will close. So, by my count, it takes 3 clicks of the mouse, if you want to use the calendar, to change to any month in the current year.

      Note the image of the calendar to the right of the calculator is attempting to get usage across.

      About dropping the ‘0’ in the date. That makes the code for handling dates a lot more complex. Having a date that is typed in always be 8 digits reduces complexity by many time, especially when supporting international date conventions.

  • Thanks for the nice article. I have a following query & will appreciate if any member can help with it.

    1) How to find the returns of an irregular inflows & outflows over a short period, lets say in 4 months? I dont want to use the XIRR as it gives the compounded annualized return, which will be misleading. I want the returns for the duration of the investment. Please consider following eg:

    Date Action Qty Rate Amount

    1/7/17 Buy 200 100 20000

    6/7/17 Buy 100 90 9000

    16/7/17 Sell 150 130 19500

    4/8/17 Buy 100 105 10500

    20/10/17 Sell 250 140 35000



    • The IRR calculator also calculates a gross percentage return. If that’s not what you are looking for, then please provide some more details.

      • Thanks Karl for your reply.

        IRR works if the period is regular, whereas I want to find the returns for irregular investments (inflows & outflows) over a short period (less than a year).

        The issue with IRR (or XIRR or CAGR) is that it provides the annualized returns, whereas I am want to find out the returns when the total period is less than a year.

        Please consider following transactions. What formula or method to use to find the returns for the inflows and outflows over a 4 month period?

        Date Action Qty Rate Amount

        1/7/17 Buy 200 100 20000

        6/7/17 Buy 100 90 9000

        16/7/17 Sell 150 130 19500

        4/8/17 Buy 100 105 10500

        20/10/17 Sell 250 140 35000



        • I’m wondering if you looked at the calculator I recommended (IRR). The user can change the dates of the cash flows. Further, you tell me what you don’t want, i.e. an annualized return, but you don’t tell me what you do want. THe linked calculator will calculate a gross return. Frankly, I don’t know what else there could be. Please explain.

          • Thanks Karl for the prompt reply.

            The IRR calculator is very nice but it provides the option to chose one of the regular cash flow frequency (month, weekly, quarterly, bi annually, annually etc) and rightly so, because that’s how IRR works.

            The issue I have is, my inflows/outflows are irregular and I want to find out the returns for the actual period. Let me explain further:

            Let’s say, I invested $20000 on 1st July 2016 and further invested $9000 on 6th July 2016. Then I sold stock and got $19500 on 16th July 2016.

            I again bought on 4th Aug 2016 worth $10500 and sold the entire stock on 20th Oct 2016 for $35000.

            Now, my total investment is (20,000 + 9000 + 10500 ) = 39500

            Total Sale value is (19500 + 35000) = 54500

            Profit = 54500 – 39500 = 15000

            If I want to calculate the return on my investment for the period I was invested in i.e. profit of 15000 made from 1st July 2016 to 20th Oct 2016 i.e. 112 days…how should I calculate that?

            Thanks and regards


          • The IRR calculator will do exactly what you want. Let me explain.

            The point of the regular cash flow option is just to setup the calculator with some dates that will most closely represent the cash flow a user needs. Once the screen is setup however, the user can change the dates easily. They can either click in the date and edit with the keyboard, or click on the calendar symbol on the right of the date and select the date from a pop-up calendar. Two things to note:

            • All dates with a 0 values, have no impact. So don’t worry about them.
            • You don’t even have to worry if the dates are not in chronological order. The calculator will sort them when the user clicks on the calc button.

            Since you are not interested in an annualized rate of return, just look at the "Gross Return".

            Please let me know if this works for you.

          • Hi Karl,

            Thanks for the latest answer. I am replying to your earlier answer because there is no reply option after your last revert. I am copying pasting your last reply and then I will update you of the outcome as you had suggested.

            “The IRR calculator will do exactly what you want. Let me explain. The point of the regular cash flow option is just to setup the calculator with some dates that will most closely represent the cash flow a user needs. Once the screen is setup however, the user can change the dates easily. They can either click in the date and edit with the keyboard, or click on the calendar symbol on the right of the date and select the date from a pop-up calendar. Two things to note:
            • All dates with a 0 values, have no impact. So don’t worry about them.
            • You don’t even have to work about if the dates are in chronological order. The calculator will sort them when the user clicks on the calc button.
            Since you are not interested in an annualized rate of return, just look at the “Gross Return”. Please let me know if this works for you.”

            I entered the dates and the amounts as suggested. The result appear wrong. Maybe I did something wrong. But I have double checked it few times already. I wish there was an option to upload the screen shot, it would have shown all the entries I made and the result I got. I am getting the following result which appear incorrect to me.

            Internal Rate of Return (IRR): -31.414%
            Gross Return: -8.403%
            Net Present Value (NPV): $0.00
            Total Invested (-outflows): $-59,500.00
            Total Returned (+inflows): $54,500.00
            Net Cash Flow (Profit/-Loss): $-5,000.00

            Thanks and regards,


          • It appears the signs (+/-) of the values are wrong. As you indicated in I believe your 2nd post, there is a profit of 15,000, which seemed right to me. Here the calculator is showing a loss of $5,000.

            The key for entering values is to enter a value with a negative for every investment (as if you are writing a check to invest) and enter a value as positive if you’ve sold the investment (as if you are putting the money back into the checking account).

            Now, my total investment is (20,000 + 9000 + 10500 ) = 39500

            Total Sale value is (19500 + 35000) = 54500

            Therefore, you should have entries that look like this (just set the dates)


            Investment return:


            If you have more questions or comments, feel free to post them on the IRR calculator’s page. I have easy access to the messages and can see the details regardless of where you post.

          • Hi Karl,

            Thanks for the reply. It worked out this time, as you had suggested.

            Earlier I made the mistake of entering the initial investment twice (first above the table and then manually added it in the table also) & hence the wrong result. Now, with right data entry, the result looks like:

            Internal Rate of Return (IRR): 581.389%
            Gross Return: 37.974%
            Net Present Value (NPV): $0.00
            Total Invested (-outflows): $-39,500.00
            Total Returned (+inflows): $54,500.00
            Net Cash Flow (Profit/-Loss): $15,000.00

            Since my inflows/outflows were irregular, XIRR in excel also gives me the same value of 581.389%

            Similarly Gross return of 37.94% also matches with the profit/total investment formula.

            Is there a way I could get exact return? Let me explain what I mean:

            1) The Profit of 15000 was made on the total investment of 39500 over the entire duration of 111 days (from 1st July to 20th Oct. i.e. first investment date to last sale date)

            2) But entire 39500 was not invested for 111 days. Rather, out of 39500, 20000 on 1st July was invested for 111 days. Similarly, 9000 on 6th July was invested for 106 days & 10500 on 4th Aug was invested for 77 days.

            2) Also, the entire profit of 15000 was not over 111 days. Rather, out of 15000, 5000 was made in first 15 days of the investment duration of 111 days and the remaining 10000 was made on the 111 day.

            So, now if I want to calculate my exact returns for the duration of my investment, how should I calculate that?

            Thanks & regards,,


          • Rahul, I think the way I would approach this is to take a weighted average of the amount invested (with days invested being used to do the weighing) and divide this amount amount by the total amount returned. Sine you know Excel, here’s how to calculate a weighted average. I’m only offering this as a suggestion. I certainly have not explored this thoroughly. Good luck.

          • Hi Karl,

            Thanks for the reply and my apologies for the late reply as I was travelling.

            Using weighted Avg was one of the approach I had thought earlier, but it doesnt factor out the time period. For time period over a year, one can use CAGR or IRR or XIRR, however, for period less than one year, one has to use absolute returns. Now, even if multiple investments (outflows) and sale (inflows) can be avg weighted, but the absolute return would still be the same, for lets say 4 months period or 10 months period.

            I dont know if I am able to explain you, what I am saying.

            I am hoping to find out if there is a way to calculate returns for multiple, uneven outflows and inflows for period less than one year. Technically speaking one can use XIRR for period less than one year, but it annualises the result to make it misleading.

            Thanks and regards,


          • Hi Rahul, about the weight average, I don’t understand what you mean by "it doesn’t factor out the time period". When I was originally looking into this, I was calculating a weight average for the number of days. But then again, I didn’t like the results. That’s why I didn’t go into more detail.

            The point of the XIRR annualizing the rate of return is so users can compare different investments. It is not about the single value and bragging rights. 🙂

          • Hi Karl,

            I meant, that the weighted avg will be same for the investment done over let’s say 4 months and 10 months. For instance, rate of return of profit of 15000 made in 4 months or 15000 in 10 months will give the same result using weighted avg.

            Thanks and regards,


  • Would anyone please help

    i am looking for calculator for saving account ie:
    Jan 1, 17 deposit $5500.00
    Jan 15, 17 depoit $3240.00
    Mar 10, 17 depoit $ 1265.01
    an so on multiple monthly deposit

    that will do compound interest ie 2.5% from Jan 1 and then 2.55% on
    example Jul 12


      • Thank you so much Sir. Thanks what i was looking for thx again

        Is it possible to download that calculator to use it offline if not any way to do that on excel

        again thx

        • Very happy to hear that the calculator worked for you.

          And yes, it is possible to download it. (This is when I get to give you my sales pitch!)

          C-Value is the same as the Ultimate Financial Calculator. It cost $49.95 and it runs on Windows computers. You’ll be able to save your entries.

  • when calculating interest due on a line of credit with a fixed monthly payment do I include date of payment in previous months calculations – date of payment fluctuates from 1 to 3 days. Thank-you.

    • Without having the terms of this line of credit, I can’t say for sure. But in general, you would have to do two calculations to confirm the interest amount due.

      Say interest is calculated on the 13th of the month and the payments are paid on the 15th. Do one calculation from the 13th to the 15th on the balance as of the 15th and a second calculation from the 15th to the 13th of the next month on the new balance after the 15th’s payment.

  • Calculator works flawless, I found it very easy to calculate the interest owed to me. Make a application for my smart watch.
    So I may take it into the courthouse.

  • Dear Karl.
    I have a need to calculate the cost of the interest being incurred on a loan to start a small business.
    My bank would never loan the amount needed of a nominal U$ 100,000 so I will be borrowing that amount privately for 24 months, and at a rate higher than the normal bank rate.
    I would like to run the loan account the same as for a standard bank overdraft account where if my understanding is correct you pay a fixed fee for having the facility available but then if you don’t ever use it or only ever used say U$ 1000 for 6 months then presumably the interest paid say at 15% would be a bit less
    than U$ 75 so you would pay back U$ 1075 during Month Nr 6

    My expenditure would begin at modest amounts like:-
    1 st expenditure $5k during Month Nr 1 for sample product.
    2 nd expenditure $15k during Month Nr 3 for material to make with
    3 rd expenditure $ 25 During Month Nr 4 for more material to make with
    1 st repayment into account $25k during month Nr 7 from first sales of product.
    2 nd repayment into account $ 25k during Month Nr 9.
    4 th expenditure $ 55k during Month Nr 10 to build a process machine;

    So gradually I would repay with earnings from manufacture from the machine but with cash flow always quite stretched due to proforma payment for raw materiel which has to be made in the US and shipped to South Africa and then waiting for probably 60 day payment from the state who is the client thus from buying material to being paid for product will be typically 120 days.

    I suppose if my investor agreed to it, then the best might be to deposit all of that U$ 100k money loaned into the bank account we create for the new company So we wouldn’t pay the bank any interest but we would still need to pay him his interest that he would have earned if he were paying us from his own interest earning account as we needed cash and as we repay him as we get paid by our client, plus whatever the difference between the bank rate and his required rate of return on the loan.

    Do commercial banks calculate your interest, both earned and incurred, hourly or daily or monthly???

    Kind regards and thanking you for your interest.
    Ken Scrutton
    Sat 23rd Dec 2017

    • Hi Ken, thank you for your question, but I’m hardly qualified to answer it. First, from your point of view, it is not so important how banks generally calculate interest as it is how your specific bank calculates interest (or those that you are considering doing business with). Secondly, I’m in the US and I gather you are banking in South Africa, so the information I have to offer could be totally irrelevant due to the difference in jurisdictions.

      If you have a question about either how to use a calculator or what calculator would be best to use for a particular calculation, then I’m more than happy to answer those types of questions.

    • It’s not always higher. For example, when the calculator load, click on the &Calc& button with the default values and both the interest rate and APY are 10.0%.

      Are you thinking it should never be higher? The APY is a calculation defined by Regulation DD of the Federal Reserve. For one thing, it specifies that a 365 day year (as I recall) be used. This means if a user sets the days per year to 360, the interest will be higher than with a 365 day year and thus the APY will be higher than the interest rate.

  • It would be nice to take into account the average annual withdrawal so that you would have a more accurate idea of how much money would be left on your bank account after a certain period of time.

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