Significant figures

You can use the following cell formula to quote a value to a specific number of significant figures.

=ROUND( value, sigFigs - ( 1 + INT(LOG10(ABS(value))) ) )

where

value is the value you want to quote

sigFig is the number of significant figures required.

An alternative

The problem with the method above is that if you have the number of decimal places for the cell set to more than your required significant figures then you'll see trailing zeros that you don't want. The following (much more complicated) formula gets over this by using the TEXT worksheet function together with an automatically generated text format statement:

=TEXT(TEXT(value,"."&REPT("0",sigfigs)&"E+000"), "0"&REPT(".",(sigfigs-(1+INT(LOG10(ABS(value)))))>0) & REPT("0",(sigfigs-(1+INT(LOG10(ABS(value))))) * ((sigfigs-(1+INT(LOG10(ABS(value)))))>0)))