Motorcycle ergonomics have always been a super tricky area to discuss, because we all have bodies that are shaped differently.
So far, the best we've been able to do is tell you our height and leg length and then let you extrapolate from our experiences on a bike. With a little logic, most people are able to figure it out, assuming they can find someone whose body isn't too different and who's ridden a variety of motorcycles.
Once you've chosen a bike and plugged in your height information, you can further customize the fit by changing the bike to reflect modifications to the handlebar, seat, or pegs, change the seating position to reflect sitting forward or back on the seat, and simulate putting your feet on the ground. Allowing you to adjust both height and leg length is a really helpful touch for those of you who, like me, are tall but are mostly torso.
Obviously, these numbers don't mean a ton without context. The best way to use it is to select a bike you've ridden that you felt fit you well, and then compare it to other bikes you're considering.
While the site looks pretty rudimentary, it appears to be fairly well maintained. Clicking "add a motorcycle" gives you the option to sort by manufacturer, look at popular bikes, or browse their most recent additions, which revealed that they last updated the site with info for the new BMWs and the Ducati Scrambler in December.
Save this one to your bookmarks under "my next bike." You all have that category too, right?