Key Concepts: Significant Figures

Core Definitions

• Significant Figures: The digits in a measurement that are known with certainty plus one estimated digit.
• Non-zero Digits: All non-zero digits are always significant (e.g., 123 has 3 sig figs).
• Captive Zeros: Zeros between non-zero digits are significant (e.g., 1002 has 4 sig figs).
• Leading Zeros: Zeros before the first non-zero digit are NOT significant (e.g., 0.0045 has 2 sig figs).
• Trailing Zeros: Zeros at the end of a number are significant only if there is a decimal point (e.g., 100. has 3 sig figs).
• Exact Numbers: Numbers obtained by counting or by definition have unlimited significant figures.