What is the ultimate strength of normal rope of 12mm diameter?

When you say "NORMAL" rope... what sort of material are you assuming?

Lets say jute.

It varies with the moisture contend but here's a chart. RopeSafety - rope_strength

Roughly 2200#, but depends on rope quality and the lay of the rope. 12mm is almost 1/2 inch and I used the formula for 1/2. Formula for natural materials is 900 X circumference squared or (1/2 X pi) squared.

Thank you very much guys.