Significant figures (sig figs) indicate the precision of a measurement. Reporting too many digits implies false precision; too few wastes information.
Counting Rules
- Non-zero digits are always significant
- Zeros between non-zero digits count (1002 has 4 sig figs)
- Leading zeros never count (0.0045 has 2 sig figs)
- Trailing zeros after a decimal count (3.50 has 3 sig figs)
Practice with the Significant Figures Calculator.
Operations
Addition/subtraction: round to least decimal places. Multiplication/division: round to fewest sig figs.
Going Deeper
Count and apply significant figure rules for lab reports and exams. This guide connects theory to practice — use the related calculators linked at the bottom to verify each example with your own numbers.
Practical Tips
- Write down given values and unknowns before opening the calculator.
- Check units and rounding rules appropriate to your context (class, lab, or business).
- Compare manual working with the calculator result to build confidence.
Common Mistakes to Avoid
- Rushing inputs without reading field labels carefully.
- Confusing similar formulas that use different variables or units.
- Reporting results with more precision than your inputs justify.
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