What are significant figures?
Significant figures are the digits in a measured value that communicate precision. Non-zero digits count, zeros between non-zero digits count, and trailing zeros count when a decimal point makes the precision explicit.
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Significant Figures Calculator
Count, round, and calculate sig figs with step-by-step explanations and lab-report-ready answers.
Step-by-step explanation
Step 1
Find the first non-zero digit. Leading zeros before that digit are not significant.
Step 2
Count the significant digits: 4, 5, 0.
Step 3
0.00450 has 3 significant figures.
Lab Report Answer
0.00450 has 3 significant figures based on the written digits and zero rules.
Rules for counting significant figures
Leading zeros are placeholders, not significant figures. Captive zeros between non-zero digits are significant. Trailing zeros after a decimal point are significant. Whole-number trailing zeros without a decimal point are ambiguous.
How to round to significant figures
Start at the first non-zero digit, keep the requested number of significant digits, then check the next digit. If the next digit is 5 or greater, round up.
Addition and subtraction rule
For addition and subtraction, the final answer is rounded to the least precise decimal place. The number of significant figures in each input is not the deciding rule for this operation type.
Multiplication and division rule
For multiplication and division, the final answer is rounded to the fewest significant figures in the measured inputs.
Scientific notation and sig figs
Scientific notation separates the measured digits from the power of ten. The coefficient determines the significant figures; the exponent only changes the size of the value.
Common confusing examples
0.00450
3 significant figures: 4, 5, and the final decimal zero.
100
Ambiguous unless written as 100., 1.0 × 10^2, or 1.00 × 10^2.
12.5 + 0.003
Report 12.5 because the least precise decimal place is tenths.