Significant Figure in Physics

The significant figures of a number are digits that carry meaning contributing to its measurement resolution. This includes all digits except:
  All leading zeros;
 Trailing zeros when they are merely placeholders to indicate the scale of the number (exact rules are explained at identifying significant figures); and
 Spurious digits introduced, for example, by calculations carried out to greater precision than that of the original data, or measurements reported to a greater precision than the equipment supports.