How to round off percentage uncertainties??? Here's is an example question: Find the percentage of uncertainty in (225.7+/-0.5)mm. I know that to find out percentage, it's simply 0.5/225.7 x 100 = 0.22153088...% Now, my question is, how much do I round off for this percentage uncertainty? Should I just round it off to one significant figure? Or Is there a certain rule?