I found a post that asked the same question. A user by the name of GoSlash27 responded to it with an equation, but I'm not sure what he means with some of the names and ways he names the unknown values (link). I would've loved to ask them what they meant with some of these definitions, but unfortunately the comment and the post are almost a decade old at this point. And, between 9 years ago and today, we've had a lot of changes, so maybe the equation is no longer correct.
That's why I'm asking any of you that knows, how can I know the maximum tons to LKO that my rocket can carry? Maybe there's a website, or perhaps an equation, but I really don't know. I'll be happy with any of your answers!