Chemistry 11 · Chemistry · Lesson 1.4
Significant figures in calculations
- Level
- Grade 11
- Reading time
- 13 min reading
- Review
- Last reviewed 2026-09-03
- Standard
- Accuracy standard
- Errata
Abstract
Counting significant figures and rounding correctly in calculations.
What are significant figures?
Short answer
Significant figures are the digits in a measurement that carry meaningful precision — all certain digits plus one estimated digit. They communicate how precise a measurement is. In calculations, the result is rounded so it is no more precise than the least precise value used: addition keeps the fewest decimal places, multiplication keeps the fewest significant figures.
Concept preview
What you will be able to do
- 01Count the significant figures in a measurement
- 02Apply the rounding rule for multiplication/division and for addition/subtraction
- 03Recognise exact (counted or defined) numbers as having unlimited significance
A significant figure is a digit that is measured or meaningful. If a stopwatch reads , that measurement has three significant figures, because the device can genuinely resolve the tenths place. Claiming the time was would be a joke — the extra digits are imagined, not measured. Significant figures therefore record not just a value but how precisely it is known: a mass written as (six sig figs) was measured on a far more precise balance than one written as (four sig figs).
School Plan
Significant figures in calculations
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Related topics
Frequently asked questions
- Are trailing zeros significant?
- Trailing zeros are significant only if there is a decimal point; 100 has one significant figure but 100. has three.
- How many significant figures does a calculation keep?
- For multiplication and division, the fewest significant figures of any value; for addition and subtraction, the fewest decimal places.