Significant Figures
Digits that carry meaning about the precision of a measurement.
Key idea
Digits that carry meaning about the precision of a measurement.
In depth
Significant figures show how precisely a number is known: all non-zero digits count, zeros between digits count, leading zeros do not. Report calculations to the precision of the least precise input.
Worked example
0.004050 has 4 significant figures (4, 0, 5, 0). 12.3 × 1.2 = 14.76, reported as 15 (2 s.f.).
Real-world uses
- Reporting lab measurements honestly
- Deciding how many digits to show on a weather or sensor reading
Common mistake
Counting leading zeros as significant.
How to learn this
- Read the key idea and say it in your own words.
- Work through the worked example, then try a similar problem.
- Use the interactive lesson’s visual and mini-quiz to check the pattern.
Frequently asked questions
What is Significant Figures?
Digits that carry meaning about the precision of a measurement. It is a topic at the intermediate level in Arithmetic & Number Sense.
Where is Significant Figures used in real life?
Real-world examples: Reporting lab measurements honestly; Deciding how many digits to show on a weather or sensor reading.
What should I learn before Significant Figures?
Make sure you are comfortable with Scientific Notation, the previous topic in Arithmetic & Number Sense.
What is a common mistake with Significant Figures?
Counting leading zeros as significant.
How can I practise Significant Figures?
Open the interactive lesson, play with the visual, then answer the three-question mini-quiz. Getting two right marks the topic complete.
What comes after Significant Figures?
Move on to Rational Numbers next.
Related intermediate topics in Arithmetic & Number Sense
- Long Multiplication – Multiply by each digit of the multiplier, shift by place value, then add partial products.
- Long Division – Divide, multiply, subtract and bring down repeatedly to get the quotient.
- Factors and Multiples – Factors divide a number exactly; multiples are its products with whole numbers.
- Divisibility Rules – Quick tests: by 2 last digit even, by 3 digit-sum divisible by 3, by 5 ends 0/5, by 9 digit-sum divisible by 9.
- Prime Numbers – A prime has exactly two positive divisors: 1 and itself.
- Composite Numbers – Numbers greater than 1 with more than two factors.