1. Every nonzero digit is significant (ex. 2317.9)
2. Sandwiched zeros are significant (ex. 404)
3. Zeros that only serve as placeholders are not
significant; can’t be dropped, show magnitude (ex.
0.0047, 0.0000000000000003, 300, 2050)
4. Zeros at the end of a number and to the right of
a decimal point are significant. (ex. 47.30, 3.0000)
5. Exact numbers have an infinite number of
significant digits. These include numbers that were
counted or are defined values (ex. 40 students, 5
pencils, 100 cm = 1 m, 12 = 1 dozen)
A
P
If a decimal point is PRESENT, start on the PACIFIC (P) side
and draw an arrow through the number until you hit a non-zero
digit. Count all numbers without an arrow through them.
If a decimal is ABSENT, start on the ATLANTIC (A) side and
draw an arrow through the number until you hit a non-zero
digit.
The United States
Of America









0.00235 g
0.0700 cm
100.23 mL
9000 mg
70.0 kPa
0.489 L
8,000,002 mm
8,000,000 m
0.0000000001 kg