If you just need to round for display purposes:

Format/Cells/Number/Scientific
Set Decimal Places to 2.

In scientific notation, 2 decimal places will always equal 3 signifiant
figures.


If you need to actually do the rounding, try this:

=ROUND(A1,2-INT(LOG10(A1)))

Tim C


"Topher" wrote in message
...
In scientific work you need to use significant figures.

A That is 0.1345 is 4 sig fig or 1.345e-1.
B But 0.01345 is also 4 sig figures or 1.345e-2.

My problem is i need to truncate to 3 sig figures and not to 3 decimal
places. How can I round and make the numbers look like:

A 1.35e-1
B 1.35e-2

Thanx for the help