The next few posts are for the newbies. Experienced kinksters feel free to comment.
Steel chain comes in five grades: 30, 43, 70, 80 and 100. The grade tells you the tensile strength of the steel used to make the chain with 30 being the weakest and 100 the strongest. Grades 30, 43 and 70 are “not recommended for overhead lifting” where the load can fall on people if the chain fails. The stronger grades will be more expensive, of course. For our purposes, looking at the “working load” of the chain is a better gauge of whether the chain is suitable. If you weigh 200 pounds and you want to suspend yourself from the ceiling while struggling, you could conceivably put shock loads up to about twice your weight on the chain or 400 pounds. If we use a safety factor of 5, then we’ll need a chain with a working load of 2,000 pounds. Looking here:
http://www.fehr.com/img/product/description/NACM%20Welded%20Chain%20Specifications.pdf
we find that 3/8” Grade 30 proof coil has a working load of 2,650 lbs. 3/8” is very heavy chain. Heavy can be nice but if you want something lighter, 1/4” Grade 43 chain has a working load of 2,600 lbs. If you went with Grade 100 chain, 7/32” chain (less than 1/4” or about the size of the light weight Grade 30 chain in the hardware store) will get you 2,700 lbs working load - at a price!
If you don’t plan on hanging from the chains, Grade 30 chain in 3/16” (800 lbs working load) or 1/4” (1,300 lbs) will work fine. A very strong man can bench press 300 pounds and put a shock load of maybe a little more than that on his wrist chains. Of course, heavy is nice. A 15-inch ankle chain made from 3/8” proof coil weighs about 2 pounds not including whatever the cuffs weigh and feels absolutely wonderful when every movement is weighted down by those massive links.