Reverse "Enter Custom Amount"

I wasn't really sure what to title this suggestion, my apologies. I would like to propose a section on the ZC purchasing page that acts as a reverse of the enter custom amount. Whether you can actually purchase via it I'm unsure (I don't know if that coding is possible), but just a calculator would be great, honestly. Let's say I have a $25 USD budget for ZC. I enter $25 into the box and it tells me the exact amount of ZC I can purchase at the moment, with the best deal. Even if it's a weird number like 1236, I think this would be super helpful. It may just be a stupid personal want, but I would be really happy to be able to say "okay, I'm going to spend X EVERY week on PFQ," instead of buying packs - because the price fluctuates. This way you can spend what you're willing to and just get however much ZC that is.

Oooh, support. I think this would be pretty helpful for people on a budget who only want to put a certain amount of money into ZC.

Support: Different currencies often have very poor conversions so this could help with actually finding out what something was worth

Little confused about this by just reading the title, but full support! It seems very helpful, even if it turns out to just be a small calculator or something.

Support! Since I use only gift card, that would help me to put x much on the site for ZC xD

Support! I have to guess and adjust a few times to get it to work out with the amount of money I wish to spend. This would be helpful.

Oof i am so guilty of wanting to spend an exact amount! Huge support! Maybe it could round to the nearest 5 or 10? (Always rounding down of course)