I wonder if any of you came across an indy that could show the lot size one could use to open a position at a specific risk level of free margin (im not sure if speak my mind clearly

What im looking for, is something that would easly and clearly tell me: hey! you want to trade EurUsd now? if you go with a 0.01 you will use 1% of whats left in the free margin, if you go with 0.1 you will use 10%... and so on.
I guess - but its a blind guess - indy would have to consider pip values, leverage and of course free margin.
Does such a thing exist?
Best regards