How many significant figures are in 163?
The rules for significant figures are:
If the number is any whole number other than 0, it counts as a sigfig.
If the number is zero, it does not count as a sigfig.
However, if the zero is in the middle of two whole numbers, then the zero counts as a sigfig. This is known as the 'captive zero'.
If there is a decimal point present, then the zeroes following a whole number counts as a sigfig. This is known as the 'tailing zero'.
Examples of captive/ tailing zeroes:
101 (captive, 3 sigfigs)
2002 (captive, 4 sigfigs)
1.00 (tailing, 3 sigfigs)
100. (tailing, 3 sigfigs)
4.004 (captive and tailing, 4 sigfigs)
Please note that zeroes in front of a whole number do not count as a sigfig regardless whether or not there is a decimal point or not.
For example, 0.0001 (only 1 sigfig, the zeroes do not count)