Amortization Calculator – Bret's Blog (2024)

Posted on November 18, 2023

Calculator Web Page Redesign

This update is long overdue.

The world of web pages has grown smaller over the years. That is, web pages are increasingly geared toward hand-held devices like phones and tablets. The design I had for so long was still targeted at desktop screens.

I published a new responsive design of the amortization calculator pages which now scale better for smaller screen sizes. For now, the color scheme is mostly the same, and the calculations themselves should not be affected. I hope you’ll not notice any serious change in behavior.

But it’s always possible that I messed something up along the way, so if something breaks for you, or if some formatting seems particularly wonky, please let me know!

Posted on June 22, 2010June 22, 2010

The Latest Addition

Over the years, a lot of people have asked for calculator features like occasional extra principal reduction payments, tracking fees or late charges, summary of interest over a fiscal year. My pat response is “this kind of thing needs a spreadsheet or special-purpose software.”

Well, I’ve taken a little time to work up a basic amortization spreadsheet. It doesn’t have all the calculation options that the web calculator provides (it only calculates the payment, for example), but the amortization schedule it produces will allow one to track extra payments and fees, to include payments for insurance and taxes, and it provides a nice fiscal year summary of interest paid.

It took a few days of playing around with Excel to get it working mostly right, and it’s free for you to download and try, if you’re into that kind of thing. Maybe it will give you some ideas about how to build your own custom spreadsheet. But of course, use at your own risk! Please don’t base any high-finance decisions on the spreadsheet’s results until you’ve verified that it’s doing everything correctly. Like the web calculator, I consider this a planning tool only!

If you want to give it a shot, here’s a link to the spreadsheet. Enjoy!

Posted on June 14, 2010

Pushing the Limits

I’ve made a few more improvements to the calculator today. Since I added some comma separators to the output to improve the readability of larger numbers, I thought I should do something about the upper bound of the calculator. Before today, the calculator couldn’t amortize amounts larger than about 21.4million. This upper bound was imposed by the computer’s native word size and how I chose to round values to the nearest whole penny. By changing the rounding procedure, I have boosted that upper bound to under 10billion. Above this value, the calculator will silently start to lose resolution at the low end, but amortizing values in the 100s of millions should be possible now.

Posted on June 12, 2010

Identifying the cross-over point

I just can’t help myself: when I start to tweak things, I start coming up with more ideas for making things a little better or easier. Nothing dramatic, just little things.

Today’s idea was to make it easy to identify that point in the amortization schedule when the principal component of a payment first exceeds the interest component of a payment. Let’s call that the cross-over point. If you run an amortization schedule now, the cross-over point is highlighted in green. There may be schedules without a cross-over point (usually shorter term loans), in which case there’s no special highlighting.

Who knows what might come next, now that I’ve started tweaking. 🙂

Posted on June 11, 2010June 11, 2010

Small Improvements

It’s been a while since I’ve made any improvements to the calculator, but today I finished a few cosmetic upgrades. The Summary section has some nicer layout and formatting, and the addition of comma-separators should make larger numbers easier to read.

Posted on October 2, 2009October 2, 2009

Even more math…

Hi, folks. It has been quite a while since I’ve made any substantial additions to the site. I just added a new document with some new formulas for directly calculating the interest portion of any payment, and for calculating the total interest paid so far. If you’re into math, you might find the Interest Recurrence document mildly useful.

Posted on October 30, 2008October 30, 2008

A little Halloween treat

I added a little Halloween decoration to the calculator page, for some holiday variety. Thanks to Don Barnett for the cool pumpkin background.

Posted on October 17, 2008

Calculator Printing and Display tweaks

I’ve made some slight modifications to the schedule display: alternating rows of the table now have color bands to help identify rows more easily. In the process, I was also able to reduce (slightly) the amount of HTML that’s generated, allowing the schedule to download and render more quickly (though this is hardly an issue for most of us these days).

For people generating hard copies, I made some very minor tweaks as well. I don’t know if it makes things any better or not.

Posted on August 10, 2008August 10, 2008

Baubles and bangles and beads

Through trial and error I have played with the calculator’s web appearance. I think it looks more attractive, and I hope you do too. I would never claim to be a graphic designer, but I do what I can.


Posted on August 8, 2008August 8, 2008

Printing Schedules (again)

Hi, folks. I’ve heard from a few of you who have said that you have difficulty printing schedules, or that schedules produce a lot of blank pages. I still haven’t experienced this problem myself because I can’t test every browser/printer combination available.

However, I have tried to make some changes to the HTML that the calculator produces. For those of you who had printing problems, please give the calculator a try now, and let me know if things have improved any (or if they’ve gotten worse, or if nothing has changed).


Amortization Calculator – Bret's Blog (2024)


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