I am trying to find a calculator to figure out roi. (or even the math formula I can use to manually figure it out)

I have been looking around and can find all sorts of calculators on everything else but not that will do what I am looking for. I am hoping someone else has come across something and can post me a link.

what I am looking to do is take my starting amount, say $250 and then at the end of each day, week, month or year type in my account balance and be able to figure my current roi.

Im sure everyone here already knows how to do this lol. maybe I knew once upon a time and have forgotten lol.

thanks in advance!