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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. More below...»

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Related: Compound Interest Calculator

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.

Related: U.S. Rule Loan & Negative Amortization

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.

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91 thoughts on “simple-interest-calculator

  1. This is exactly what I needed to calculate interest for an account that is past due. I work in the legal field and needed to find out what would be owed to date on a previous judgement.

    • This is perfect – Exactly what I needed to calculate interest on my monthly invoices. I used it on my job. Thanks

  2. Teaching kids about the various methods of interest solutions/problems applied, fantastic.

  3. I owe my brother some money and needed to figure the interest too. Thanks!

  4. It would be helpful if this calculator could also generate an amortization table for monthly payment amounts.

  5. This works if you are receiving one lump payment but it does not if you have multiple or more than one payment.

    Do you have a calculator for that?

    • Yes, I’m sure I do.

      But I’m not 100% sure I’m clear on what you mean. You use the word "payment." Is this a loan cash flow, and the balance is approaching 0? If so, then try this loan calculator.

      Or is this a savings or investment cash flow and the balance is growing? Then try this savings calculator.

      You can also try this time value of money calculator. This one is the most flexible. It works with both loans and investments. Scroll down the page for 25 tutorials.

  6. Works great! Do you have a calculator for calculating simple interest when monies are borrowed at different times? (i.e. one loan but two advances of money…and yes, I know I could just calculate them separately but was wondering if you had a program for doing it in one step)

    • Yes.

      Please see this calculator.

      Basically what you’ll do is enter the two loans in the first two rows with their dates.

      Then in the 3rd row, set it for payment and the amount as "Unknown."

      Scroll down the page to the tutorials. If you want the payment to reflect just the interest amount, that can be done too by setting it as an interest only series.

      If you have any questions just ask.

  7. Personal reasons. I invested some capital in equity so cash-flow is on the low side. Whenever I’m late on payements for whatever expenses, I componsate my crediteur in order to meet eachother halfway. This site is very helpfull for quick calculations.

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