How Many Significant Figures Are in 100.00?
100.00= 5 significant figures
Why 100.00 has 5 sig figs
100.00 has a decimal point, and all trailing zeros after a decimal point are always significant. The digits 1, 0, 0, 0, and 0 are all significant — giving exactly 5 sig figs. Writing 100.00 instead of 100 is a way of explicitly communicating high precision.
Rule applied
Trailing zeros after a decimal point are always significant (Rule 4). See full rule →
Edge case note for 100.00
Compare: 100 has 1–3 sig figs (ambiguous). 100.00 always has exactly 5. The decimal point is what makes the difference.