Significant Figures
Significant figures show the precision of a measurement.
About this topic
Significant figures show how precise a measurement is. Non-zero digits and zeros between them count; leading zeros do not; trailing zeros count only if there is a decimal point. In multiplication and division, the answer has as many significant figures as the least precise input; in addition and subtraction, it matches the fewest decimal places.
The reason is simple: a result cannot be more precise than the tools that produced it. If you measure a length as 12.3 cm and a width as 4.1 cm, the area calculator shows 50.43, but because 4.1 has only two significant figures you must report 50 cm squared. Scientific notation removes ambiguity: 4.50 x 10^3 clearly has three significant figures, while 4500 may have two to four.
Counting examples: 0.00450 has three significant figures, 100.0 has four, and 100 has one. Exact numbers, such as 12 eggs in a dozen or defined conversions like 100 cm in a metre, have unlimited significant figures and never limit your answer. Round only at the end, keeping extra digits in intermediate steps.
Students often copy every digit from a calculator, or round too early and drift away from the right answer. Treat sig figs as honesty about uncertainty: they tell the reader how much to trust your measurement in labs, medicine doses and engineering.
Key ideas
- Non-zero digits count
- Captive zeros count
- Leading zeros do not
Quick check
Use cases: where Significant Figures helps
- Homework: review the key idea behind Significant Figures before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Significant Figures without notes.
- Visual learning: play with the interactive lab to see how Significant Figures changes when you adjust its inputs.
- Teaching a friend: explain Significant Figures in your own words, then compare your version with the key ideas.
Chemistry explains medicine, food, cleaning products, fuels and building materials.
Frequently asked questions
What is Significant Figures?
Significant figures show the precision of a measurement.
What will I learn in Significant Figures?
Non-zero digits count. Captive zeros count. Leading zeros do not.
Is Significant Figures part of Chemistry?
Yes. It is one of 150 Chemistry topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Significant Figures lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Significant Figures?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.