Significant Figures Calculator
Count the number of significant figures in any number and see which digits are significant. See also Rounding Calculator and Scientific Notation Calculator.
How to Count Significant Figures
Significant figures (sig figs) are the meaningful digits in a number that contribute to its precision. To count them: (1) All non-zero digits are significant. (2) Zeros between non-zero digits are significant. (3) Leading zeros are never significant. (4) Trailing zeros after a decimal point are significant. (5) Trailing zeros in a whole number without a decimal point are ambiguous.
Significant Figures Rules
Rule 1: Non-zero digits are always significant
Rule 2: Zeros between non-zero digits are significant
Rule 3: Leading zeros are NOT significant
Rule 4: Trailing zeros after decimal ARE significant
Rule 5: Trailing zeros in integers are ambiguous
Example
Number: 0.00340
Leading zeros (0.00): NOT significant
Digits 3, 4: significant
Trailing zero after decimal (0): significant
Total significant figures: 3
Scientific notation: 3.40 × 10⁻³
Frequently Asked Questions
Why are leading zeros not significant?
Leading zeros only serve as placeholders to show the position of the decimal point. They do not reflect the precision of the measurement. For example, 0.005 has 1 sig fig — the 5.
Are trailing zeros significant in 1500?
It depends on context. Without a decimal point, 1500 could have 2, 3, or 4 sig figs. Writing it as 1500. (with a decimal) or 1.500 × 10³ makes the precision clear.
How do sig figs apply to calculations?
For multiplication and division, the result should have the same number of sig figs as the input with the fewest sig figs. For addition and subtraction, the result should match the least precise decimal place.
Is the number 0 significant?
The number 0 by itself has 1 significant figure. Zeros can be significant depending on their position — between non-zero digits or trailing after a decimal point.