Accurate Compound Interest Calculator
This compound interest calculator calculates interest between any two dates. A dozen compounding periods 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 periods, 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
Information
Compound Interest
Compound interest means that interest gets paid (or is earned) on previously unpaid interest.
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Pick a Date
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 account 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.
Enter an amount and a nominal annual interest rate.
Date Math: The number of days between the dates will get calculated when you change either date. If you enter a positive value for the number of days, the end date will be updated. If you enter a negative value for the number of days, the start date will be updated.
The above means you can calculate interest for a specific number of days and not worry about what the dates are. If you need to know the interest for 31 days, then enter 31 for the number of days and don't worry about the dates.
Set the compounding and days-in-year. Click "Calc." Interest and future value are calculated (FV is starting amount plus the interest.) Depositors should use the Annual Percentage Yield (APY) calculation for comparing deposit accounts. It is the rate institutions must quote in the US for interest-bearing accounts. The Consumer Financial Protection Bureau defines APY in the Truth-in-Savings Act.
Interest may be calculated based on a unit of time, say a month. This is known as "Periodic Interest" In that case, a month's interest is always the same for the same interest rate and same principal balance regardless of the length of the month. Given $10,000 principal and an interest rate of 6.75% the interest will be the same for February as it is for March. Note if you select a periodic method such as "weekly", "biweekly" etc., and if the dates enter do not equate to a number of full periods, then interest will be calculated for the fractional period by counting the days and calculating simple interest. This generally results in 1/2 a month's interest being less than 1/2 of a full month's interest when using monthly compounding.
There is also "exact day interest." Interest is calculated based on the number of days. In this case, the amount of interest will be different for February and March. Set compounding to "continuous", "daily" or "simple" for daily interest calculations.
John says:
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.
Karl says:
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!
Dale says:
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
Karl says:
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.
Dale says:
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.
Karl says:
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:
G. Franklin says:
Hello, Karl,
I’m having trouble putting new dates into your compound interest calculator. I see that the comments here are from 2019. But I used the calculator just this December. Can you help?
Thanks!
Karl says:
Hi, what type of problem? Do you get an error message? What browser are you using? I just tried entering both dates and I’m not having an issue. I typed and date in as well as used the pop-up calendar.
By any chance did you change the date format? The calculator allows dates to be entered using one of 3 conventions: MM/DD/YYYY, DD/MM/YYYY, and YYYY-MM-DD.
G. Franklin says:
I tried both. And it had worked in the past.
Must be my local gremlin, which keeps me supplied with daily “aargh!” moments.
But all’s well that ends well.
Next time I have to use it, it’s likely to work, especially if I’m under no deadline!
Be well, and thanks again.
G. Franklin says:
Thanks for your response, Karl,
I certainly do appreciate your answering so quickly.
It wasn’t the format, but that I was hoping to put in dates from the past and the program only allowed me to input dates as of 2/1/21 forward. I wanted to start in 2015 to 2021.
I found a “work-around” by calculating the number of days between my 2015 and 2021 dates and putting those in as their equivalent in 2021 (e.g. 02/01/21 to 02/22/26).
Does your program add the extra day in February for leap years? I assume it does since it’s calendar based by specific years.
Thank you for providing this great tool to the public! I’d have been lost without it.
Karl says:
You’re welcome.
Yes, the calculator knows about leap days.
You should be able to enter any date starting with Jan. 1, 1970. I just confirmed this as well. Not sure why it would not be working for you. Are you using the calendar or typing in the dates?
G. Franklin says:
I tried both. And it had worked in the past. Must be my local gremlin, which keeps me supplied with daily “aargh!” moments.
All’s well that ends well. Next time I have to use it, it’s likely to work, especially if I’m under no deadline!
Be well, and thanks again.
Nancy says:
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?
Karl says:
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.
Nancy says:
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??!!
Horatio says:
Same problem.
Karl says:
Hello, AccurateCalculators.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.
Karl says:
Hello, AccurateCalculators.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.
Horatio says:
There are no financial calculators available
Error message: Financial Calculators – These calculators are not toys.
Karl says:
Hello, AccurateCalculators.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.
Rob says:
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.
Karl says:
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 🙂 ).
John Zhu says:
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?
Karl says:
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.
Rikhil says:
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.
Karl says:
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.
Rikhil says:
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.
Karl says:
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.)
BHUPEND says:
SUPERB CAN WE DOWN LOAD IT ON EXCEL
Karl says:
No, this is a standalone calculator.
AMir says:
Annual Interest rate (%) given by Bank0.08250 = 8.250%
Number of Period (months*years)365
Monthly Interest Rate (%) per month0.0002 = 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%
Karl says:
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?
Karl says:
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?