Writing a mortgage calculator 2


So for anyone who read this thread, I wrote a mortgage calculator as my first web development project a while ago (it’s not online any longer). I wasn’t happy with my efforts that time so I set about rebuilding the whole thing from the ground up. Well, I put the new site online tonight. You can find it here: Mortgage Calculator.

Some of the new stuff:

  • You can set deferred or interest only mortgage starts, skipped months and lump sum payments. I’ll be bringing more features in this vein soon.
  • Mortgage Interest Relief
  • Stamp Duty
  • There’s a pure html backbone behind everything so you can visit the site on the crappest of browsers (or your phone for example) and most features will still work.
  • Better Charts
  • You can email results
  • You can generate a “mortgage report card” like this:
    More details at our Mortgage Calculator

The idea being that you can easily link to one on a forum when people ask questions such as “how much will my payments be if xyz?”.

  • Plain english and concise results

As before, I’d love to hear advice, criticism, suggestions etc. I’m not even close to finished with the project and I have a long roadmap planned out in my head for it. It’s taken me 4 months to get this far though!

If you like it and you think it might be of use to other people, I’d really, really appreciate some exposure in the usual forums etc. around the place: AAM (Everyones banned… I know! :smiley: ), Daft, boards.ie etc. (Don’t spam them obviously, I just mean maybe reference the calc if your answering a mortgage related question). This would really help the site grow and motivate me to keep improving it.

Looking forward to your comments.


Well it’s a fairly basic calculator at the moment isn’t it. It just tells you what your overall interest repayment is.

I can’t see any of the other features you list. Just the plain calculator with 4 fields and the Calculate button…


Oh sorry, I see there are other options when you hover over Summary, having done your initial calculation.
You may need to make that more obvious with click buttons for the various options.

Also, why can’t I enter more than 50% of purchase price as a deposit?


You mightnt need a mortgage calculator moving forward as cash will be king and banks lending will be like hens teeth. :open_mouth:


You know you’re actually the second person that’s mentioned to me that they didn’t notice the drop down for the other options straight away. It’s definitely something I need to make more obvious and possibly change completely.

One of the hardest things to get right is balancing the user interface design so that it’s complicated enough to be able to have tons of features and input fields accessible in a small space but also basic enough so that people who only want to use basic features aren’t overwhelmed by a myriad of controls.

I’m considering moving towards a “goal centred interface” so that instead having various pages of input fields with arbitrary names like ‘basic’ or ‘extended’, I instead ask the user what they want to to eg. “Calculate the effects of a lump sum payment” or “add mortgage interest relief to these results”, and then give them the fields they need to accomplish their goals. I think this might simplify things.

About the 50% thing, I just arbitrarily set it to that value a long time ago before I put it online. It seems way too low now that you mention. I’ll bump it up to 95% tonight. Should be easily done.


I’m trying to get in at the bottom and catch the next housing bubble :smiley: You know the Irish will never give up on the property market!


I thought it was pretty good tbh - I recommended it to friends of mine who also found it great.


I never hear about this before.