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Compound Interest Calculator Savings, Investment or Loan Interest Calculations

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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


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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 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.

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53 Comments on “Compound Interest Calculator”

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  • Hello Sir, i was trying to calculate compound interest for years that are in decimal. For example, if we assume we invested $100 at a 26% rate compounded annually for 1195 days and i use this basic excel formula =100*(1+26/100)^(1195/365) and result is 213.1132 and if i do the same calculations in your calculator it shows 214.14, please help to explain the difference.

    Thanks in advance 🙂

    • Hi, I don’t get involved in the details of the calculations. If I were to do that, I would not have time to work on the website. 🙂

      However, if you want annual compounding, you have an error in your equation. The 1195/365 treats every day as the same. But for annual compounding, you have 3 years and 100 odd days (or 3 years and 99 odd days depending on the dates).

      Use the calculator with these inputs, and you’ll see what I mean. They both are for 1,195 days, but they give different results, due to one date range includes leap year.

      March 23, 2020
      July 1, 2023
      Result: 214.29 (no leap day)

      and

      March 24, 2021
      July 1, 2024
      Result: 214.14 (with a leap day)

      Keep all other details the same, including the annual compounding.

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