Mobile-friendly interest calculators - feedback welcomed

[csprof]

I got sick of the 1990s-era interest/retirement calculators out there, so I threw three little hacks online in case they were useful to anyone other than myself:

https://www.angio.net/finance/calc.html

They're designed to be fast and work well on my #@*ing phone, and just do basic things (forward, backward, contribution amount), but I'd love feedback if anyone finds them useful.  They need a little UI polish.

[arebelspy]

Nice!

The calculation I use a lot, personally is calculating a particular interest rate based on pv, contributions, fv, and time period, if you're looking to add more.  :)

Well done.

[csprof]

Nice!

The calculation I use a lot, personally is calculating a particular interest rate based on pv, contributions, fv, and time period, if you're looking to add more.  :)

Well done.

You mean that you want to determine the necessary interest rate to achieve the fv (or, put differently, "I now have $1m and I put 1000 in the bank every week for five years, and started with $10k in the bank, so what was my effective interest rate over that period?")

I like it.

[arebelspy]

Yeah, exactly.  :)

[csprof]

Yeah, exactly.  :)

Added - thanks for the idea.  I hadn't even realized I wanted it, but I did.  Now I just fear calculating my returns...

[arebelspy]

Neat, thanks!

[csprof]

Just noting for posterity - it's now https-friendly (I assume nobody cares) and a bit faster.  I've updated the original URL to point to the https bit.  Shouldn't matter much, since it's a purely client-side calculator and doesn't send any information to the server.

[pbnj]

Thank you , csprof; I found these very useful!