BeginnerTopic 2 of 104Engineering Mathematics
Significant figures
Digits that carry measurement meaning; results should not claim more precision than the least precise input.
In depth
Significant figures are the meaningful digits of a measurement: all non-zero digits, zeros between them, and trailing zeros after a decimal point. In multiplication and division the result keeps as many figures as the least precise input; in addition the decimal places of the least precise value rule.
Key points
- Leading zeros never count
- Round only at the end of a calculation
- Exact counts and defined constants have unlimited figures
Example3.20 m × 1.5 m = 4.8 m², not 4.800 m².
What is Significant figures?
Digits that carry measurement meaning; results should not claim more precision than the least precise input.
Why is it important to understand significant figures?
Calculated results must reflect the precision of the measurements they come from, otherwise a report looks more accurate than the instrument really is.
How many significant figures should I keep in a final answer?
Keep no more than the least precise input has, and usually round to one extra digit during working and round only at the end.
Are trailing zeros significant?
Yes, if there is a decimal point. 2.50 has three significant figures, while 250 is ambiguous without a note or scientific notation.
How is Significant figures used in practice?
Typical applications include reporting a load test result with the right number of digits, checking that a spreadsheet average does not overstate precision and writing a datasheet value with a sensible tolerance.
What should I learn before Significant figures?
Study "Number systems" first (topic 1 of 104 in Engineering Mathematics). It covers the groundwork this topic builds on.
What are the key points of Significant figures?
Leading zeros never count. Round only at the end of a calculation. Exact counts and defined constants have unlimited figures.
Can you give an example of Significant figures?
3.20 m × 1.5 m = 4.8 m², not 4.800 m².
What comes after Significant figures?
The next topic is "Units and dimensional analysis", which builds directly on this one.
How difficult is Significant figures?
It is classed as Beginner in Engineering Mathematics (topic 2 of 104). It is an entry-level topic. It relies only on basic school mathematics and the ideas introduced earlier in this discipline.