Posts

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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!

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Too Long Gone

The blog is long overdue for an overhaul, so I put in a new theme today. Maybe someday soon I’ll get around to some other changes. For now, I’ll just appreciate that the blog, at least, is more mobile-friendly. Cheers!

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A New Addition to the Website

I love programming, and I love to sink my teeth into a problem. Recently, I became intrigued by the Skew-T/ln p charts that meteorologists use to graph weather balloon soundings. I couldn’t find a blank graph online that completely satisfied my high-quality printing expectations, so I decided to create one myself. If you’re a closeted weather geek, or if it’s your main thing, you might find this resource useful to you. Let me know if you like it, or if you think something could be improved. You can find the Skew-T link here.

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In Passing

A good friend of mine died today. His friendship was of a rare kind, built from scratch in full adulthood, without benefit of youthful energy or shared childhood history or common locality, built even without having met face-to-face. And yet it was a solid friendship, having outlived the length of time it takes to tell all our most interesting stories.

We met online through some forum or other, finding that we shared a few interests in common. And when we each moved on to other fora, we kept our communication going through e-mail and then daily interactive chat sessions, discussing the news of the day, sharing our triumphs and frustrations. I looked forward to meeting my friend in person one day, at last being able to attach a voice to the words we’d type back and forth.

My friend actually passed away a week ago. I didn’t find out until just this morning. The week-long silence in our conversation is no longer a mystery, and the least-expected explanation for that silence has been instantiated. The loss of this friendship in cyberspace hurts as much as any friendship I have lost out here in the real world. Had I known about it in time, I would have traveled to his memorial service.

I guess we’ll just have to wait a little longer to meet up, my friend. TTYL, Curt.

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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!

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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.

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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. 🙂

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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.

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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.