Hey @kellymy
I’ve got this basic stamp calculator up now, I’ll continue to improve it (make it prettier, better user experience, etc.)
here it is for now 
https://stamp-calculator.netlify.app/
Here’s how to use it:
You can enter the current price of an international stamp, then the price you do not want to exceed. You can enter the maximum number of stamps you want to use and then add as many stamps as you can think of/want to use with the Add Another Stamp button. In each stamp field, enter the price, then a space, then the name of the stamp Then just click Calculate.
Again, I will continue to improve the site, but I wanted to get something up for the January price increases
EDIT: made this post