How Many Significant Figures Are in 0.00340?
0.00340= 3 significant figures
Why 0.00340 has 3 sig figs
0.00340 has leading zeros (0.00) and then the digits 3, 4, and 0. The leading zeros are never significant — they are just placeholders showing the size of the number. The digits 3 and 4 are non-zero and always significant. The trailing zero after the decimal (the final 0 in 340) is significant because it appears after a decimal point.
Rule applied
Leading zeros are never significant (Rule 3). Trailing zeros after a decimal are always significant (Rule 4). See full rule →
Edge case note for 0.00340
In scientific notation: 3.40 × 10⁻³ — the coefficient clearly shows 3 sig figs. The two leading zeros from the original number disappear entirely.