[Andrew]

Machinery's Handbook has all the chain formulas you could want, plus an explanation. Units are usually in chain pitches.

But...
Chains have tolerances associated with the links. As your chain gets longer, the tolerance stack up makes the chain center distance formula less accurate. Even for a moderate tolerance, the droop in a chain will be too much. Idler sprockets, tensioners, rubbing blocks become a must.

Chains also wear with use. So, even if you get the center distance correct in the first place, over time, you will start to see increasing loopiness.

In short center distances (say 2" to 6") you won't see these effects too drastically. But, in longer distances, the situation gets worse and worse.

With the push towards multi-drive motors in a drive system, we have gone with direct drive on all of our wheels over chain drive. We take a hit in the weight department, but we gain in the reliability department and in the manufacturing department.