Originally Posted by
mack_turtle
there is no formula. I've not found anything more simple the method described on this
Park Tool page. I know "engineers" think everything can be broken down to a theoretical equation, but mechanics don't waste their time with that. the only way to do it right is to do it on the bike. measure twice, cut once.
PARK shows an equation in the link you provided.
Personally, it's much easier to just wrap the chain around a ring & cog then take time to measure, write down numbers and do the math.
I wouldn't really trust a measurement from axle center to crank center to be THAT precise when juggling a snaky tape measure. I'm very far sighted (with a lazy eye to boot), old & a bit shaky. A monkey can wrap a chain.