Beginner Topic 881 of 1102 Analytical, Lab & Spectroscopy
Significant Figures
Digits in a measurement that carry meaning about precision.
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In-depth explanation of Significant Figures
Significant figures are the digits in a measured or calculated number that carry meaningful information about its precision. All nonzero digits are significant, zeros between nonzero digits are significant, and trailing zeros are significant only when there is a decimal point, while leading zeros are never significant. When multiplying or dividing, the result is reported with the same number of significant figures as the measurement having the fewest, and when adding or subtracting it is reported with the fewest decimal places. Reporting more digits than the instrument can resolve falsely implies high precision. Exact counted values, such as the number of cells in a sample, have unlimited significant figures.
Going deeper: Significant Figures
Key ideas: Count digits from the first nonzero digit to the last digit allowed by the instrument. In multi-step work keep one or two extra digits and round only at the end. For logarithms, the digits after the decimal point in the log equal the significant figures in the original number, so pH 4.25 has two. Scientific notation removes ambiguity in trailing zeros.
Common mistakes and connections: Students round after every intermediate step and drift in the last digit, or apply the multiplication rule to addition. Another error is quoting 25 mL from a burette that reads to 0.01 mL, which discards information. Defined conversions such as 100 cm per m are exact and should not limit the answer. Related to precision, error propagation and scientific notation.
Visualization of Significant Figures
Counting significant figures: leading zeros never count, zeros between digits do, and trailing zeros count only with a decimal point or scientific notation. The interactive lesson shows this as a live animation or chart.
Worked example and use case
12.0 x 3.456 = 41.472, reported as 41.5 because 12.0 has three significant figures.
Frequently asked questions about Significant Figures
What is Significant Figures?
Digits in a measurement that carry meaning about precision.
Is Significant Figures a beginner, intermediate or advanced topic?
Significant Figures is a beginner topic in Analytical, Lab & Spectroscopy. It needs no earlier chemistry lessons and is a good starting point.
What should I learn before Significant Figures?
Study these earlier topics in Analytical, Lab & Spectroscopy first: Laboratory Safety, Chemical Hazard Symbols, Measurement and Units.
What comes after Significant Figures?
The next topics in Analytical, Lab & Spectroscopy are Accuracy and Precision and Scientific Notation.
Can I practise Significant Figures with quizzes?
Yes. The interactive lesson includes a self-check question on Significant Figures, and the Analytical, Lab & Spectroscopy quiz draws on every topic in this area.
Where Significant Figures fits in Analytical, Lab & Spectroscopy
Significant Figures is topic 5 of 99 in Analytical, Lab & Spectroscopy.