Loan Calculator Script Required

[FONT=Verdana]I’m looking for a loan calculator script to use on a site. I’ve come across a few, but I need this to work the opposite way round to a typical calculator. On the ones I’ve seen, you input the amount you want to borrow and the repayment period, and it calculates the total interest and the amount of the weekly or monthly instalments. What I need is one which allows you to input the amount of the weekly or monthly instalment, specify whether that’s including or excluding interest, and the script calculates the period of the loan and the total interest payable. (Having two calculators - one for amount including interest and one for amount excluding interest would be fine, if that’s easier. :))

Any ideas?[/FONT]

It may be better to get someone to write a script that does specifically what you want. Presumably this is for a client that will be paying?

[FONT=Verdana]I rather thought that might be the case.

Unfortunately, no. It’s for a very small non-profit, and I’m working on the site pro bono, as they can’t afford to pay me, never mind somebody to write a script. Hence my question. :slight_smile:

Interest calculations involve five things - amount borrowed, repayment amount, repayment frequency, repayment period and interest rate. To calculate any one you need to have the other four. From your original post it sounds like you want it to be able to calculate two of them given the other three which isn’t possible.

I already have two different loan calculators at and so could probably add a third without too much trouble provided that it is clearly defined as to which four of the five need to be entered and which of the five is to be calculated.

[FONT=Verdana]Thanks for the reply, Stephen. There are basically four options people can choose. In order of popularity, these are:

  1. Borrow X, repay (Y+interest) each week e.g. Borrow £200, repay £5 + interest per week.
  2. Borrow X, repay Y (including interest) per month e.g. Borrow £500, repay £50 total principal and interest each month
  3. Borrow X, repay (Y+interest) per month
  4. Borrow X, repay Y (including interest) per week

In 1 and 3, the period of the loan is easy to calculate - X/Y weeks/months. In 2 and 4, it’s more problematic. The interest rate is 1% per 30 day month, APR 12.68%.

The purpose of having the calculator on the website is to give people an indication of how much interest they would pay over the period of a loan, to show how affordable these rates are by comparison with others. Even having a calculator that only deals with option 1 would be a significant improvement on what we have now. :)[/FONT]

I have just uploaded a loan period calculator (PHP and JavaScript) to

If you make the interest rate a hidden field with value=“12.68” and just have two radio buttons for monthly (with value=“12.167”) and weekly (with value=“52.143”) then you would have your options 2 and 4 covered.

If you set the interest rate to zero it would calculate the periods for options 1 and 3 but would not calculate the additional amounts required to be paid to cover the interest.

The full code (including my other two loan calculators) can be downloaded from

Each of these calculators uses JavaScript for the calculation if JavaScript is enabled and reloads the page using PHP to do the calculation if JavaScript is disabled.

Hope that this helps.

Thank you very much - that’s great. :slight_smile:

Iam A Owner of a financial site. I will suggest you to use Microsoft Excel for Loan & interest rate calculation. Its very easy, Use the Basic Laws of Financial Calculation like Annuity Calculation ruls or interest rate calculation. Than You can easily Find out the results. Its Realy Effective Than using other Software, Its My Personal Suggestion.