Significant figures

[nightguy]

How do I round a number to, say, 3 significant figures?

e.g.

123456 goes to 123000
123654 goes to 124000

1234 goes to 1230
1245 goes to 1250 (round upwards)

123 goes to 123 (unchanged)
1.234 goes to 1.23
0.0001234 goes to 0.000123

I think you can do it by taking logs and using the ROUND function, but is there a more direct method?

Thanks!

 

[Steve Hartman]

=ROUND(A1,A2-1-INT(LOG10(A1)))

where A1 is the number to round and A2 is the number of signficant digits to round to.