Significant Figures Rules

Non-zero digits are always significant.
Leading zeros (0.00...) are never significant.
Captive zeros (between non-zero digits) are always significant.
Trailing zeros after a decimal point are significant (3.00 = 3 sig figs).
Trailing zeros without a decimal point are ambiguous (100 = 1 sig fig by convention).
Trailing zeros with decimal: 100. = 3 sig figs (the decimal point makes them significant).
Scientific notation: All digits in the coefficient are significant (1.00 × 10³ = 3 sig figs).

Significant Figures Practice

Count the significant figures or round to the specified number of sig figs.

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