Significant Figures
Significant figures count the meaningful digits in a number starting from the first non-zero digit, used to round sensibly.
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Significant figures count the meaningful digits in a number starting from the first non-zero digit, used to round sensibly.
- Leading zeros are not significant
- Round at the chosen figure and look at the next digit
- 0.004562 to 2 s.f. is 0.0046
🧠 Quick quiz
Three questions. Score 2 or more to complete the topic.
What is Significant Figures?
Within Mathematics, which covers numbers, algebra, geometry, trigonometry and statistics from first principles to exam level, this topic explains Significant Figures. Maths builds step by step, so each topic here gives you a rule, a picture and a quick check you can use on homework and in exams.
Check that you can explain Significant Figures in your own words and give one example from everyday life. If you can do that, you have understood the core idea.
Understanding Significant Figures gives you a reliable method you will reuse in later maths units, in science lessons and in data work.
Significant Figures in detail
Significant figures count the digits in a number that carry meaning, starting from the first non-zero digit. In 0.004,07 the significant figures are 4, 0 and 7, giving three. Zeros between non-zero digits count, while leading zeros do not.
To round to a given number of significant figures, find the digit in that position, look at the next digit and round up or down, keeping zeros as placeholders where needed. Scientists and engineers use significant figures to show how precisely a value is known, and they stop answers from looking more accurate than the data allows.
How the interactive helps you understand Significant Figures
Click a step, or use the Previous and Next buttons, to move through the sequence one stage at a time. Auto-play moves on for you.
Before you change anything, predict the result. Then change one value at a time and check whether your prediction was right. This is a quick way to build a correct mental model of Significant Figures.
Real-life uses and examples
- Use Significant Figures when comparing prices, discounts or recipe quantities in everyday life.
- Explain Significant Figures to a friend with a simple picture, such as a row of tiles or a bag of sweets.
- Spot Significant Figures in exam questions, where it often sits inside a short word problem.
Common mistakes to avoid
- Forgetting units, signs or brackets when you apply Significant Figures.
- Memorising the steps for Significant Figures without checking why they work.
- Learning the definition without testing it. Use the quiz and the interactive to check that you can apply the idea.
Frequently asked questions about Significant Figures
What is Significant Figures?
Significant figures count the meaningful digits in a number starting from the first non-zero digit, used to round sensibly.
What are the most important points about Significant Figures?
The main points are: Leading zeros are not significant; Round at the chosen figure and look at the next digit; 0.004562 to 2 s.f. is 0.0046.
Why is Significant Figures useful?
Understanding Significant Figures gives you a reliable method you will reuse in later maths units, in science lessons and in data work.
How can I practise Significant Figures?
Open the interactive at the top of this page and change the controls one at a time. Predict the result before each change, then take the three-question quiz. A score of two or more marks the topic as complete on this device.
Which topics are related to Significant Figures?
Related topics in Mathematics include Sequences, Fibonacci and Special Sequences, Expanding Brackets.