A feature filled WordPress interest calculator

Amortization and Annuity Payments

The pro version of the plugin offers the option to calculate repayments using the standard annuity formula:

P = rC / (1 – (1 +r)-n)


P = repayment amount
r = interest rate per period (as a decimal, eg: 2% = 0.02)
C = Current loan amount
n  = number or repayments

However, there are two methods of calculating the interest rate per period. The simple method is to divide the APR by the number of periods per year. This is the system used in the USA. The method used in Europe is to convert the APR to get the rate per period. The plugin offers options for both methods.

The example below uses the US method of calculating amortization repayments:

£1,000 £10,000
1 year36 years
Your monthly repayments will be at
Total you will Pay:

Change the settings and compare with the results on this page: amortization-calc.com or bankrate.com

This example uses European method of calculating amortization repayments:

£1,000 £10,000
1 year36 years
Your monthly repayments will be at
Total you will Pay:

Test the calculations in Europe using this: moneysupermarket.com. or mortgagecalculator.net

For more information on the annuity formula take a look at the Wikipedia page.

  1. Elvin on 30 Mar 2020:

    May i know why I can’t select the Amortisation option in settings?

    Reply to Elvin

    • Graham on 30 Mar 2020:

      You need to upgrade to use that option

      Reply to Graham

  2. Sverker Weissglas on 03 Jan 2020:

    I am afraid I must be doing something wrong here… I just payed for the “pro” version in order to gain the Annuity Payments feature. However I try the plugin seems to calculate some scary math! Please tell what I am doing wrong!

    When I am at it, this is what I really want. I have read and tried for a few hours but I am stuck… maybe it’s my language limitations:

    Ideally I would like to have a form with three customer fields: a) full price b) – trade in c) -cash payment and the automated sum below = loan.

    There should be a loan period of 1-6 years (displayed in months), and the monthly cost + total displayed, (for both annuity loan and linear amortization).

    I would be very grateful for your help!

    Reply to Sverker Weissglas

    • Graham on 03 Jan 2020:

      Hi Sverker,
      Try setting the repayment divider to 12.

      Reply to Graham

  3. Bob on 10 Dec 2019:

    Hi there,
    Could we email you an example of the mortgage calculator which we’d like to replicate so that you could tell if you could do and how much you’d charge for it?

    Reply to Bob

    • Graham on 10 Dec 2019:

      Hi Bob,
      I can take a look for you. I might even have one I made previously you can use. I’ve sent you an email so you have mine (if that makes sense).

      Reply to Graham

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