Significant Figures (Edexcel International A Level Physics)

Revision Note

Katie M


Katie M



Significant Figures

  • Significant figures must be used when dealing with quantitative data
  • Significant figures are the digits in a number that are reliable and absolutely necessary to indicate the quantity of that number
  • There are some important rules to remember for significant figures
    • All non-zero digits are significant
    • Zeros between non-zero digits are significant
      • 4107 (4.s.f.)
      • 29.009 (5.s.f)

    • Zeros that come before all non-zero digits are not significant
      • 0.00079 (2.s.f.)
      • 0.48 (2.s.f.)

    • Zeros after non-zero digits within a number without decimals are not significant
      • 57,000 (2.s.f)
      • 640 (2.s.f)

    • Zeros after non-zero digits within a number with decimals are significant
      • 689.0023 (7.s.f)

  • When rounding to a certain number of significant figures:
    • Identify the significant figures within the number using the rules above
    • Count from the first significant figure to the specified number
    • Use the next number as the ‘rounder decider’
    • If the decider is 5 or greater, increase the previous value by 1

Worked example

Write 1.0478 to 3 significant figures

Step 1: Identify the significant figures

They are all significant figures

Step 2: Count to the specified number (3rd s.f.)


Step 3: Round up or down

1.05 (3 s.f)

Exam Tip

An exam question may sometimes specify how many significant figures the answer should be, make sure you keep an eye out for this, as a mark is often given for that!

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Katie M

Author: Katie M

Katie has always been passionate about the sciences, and completed a degree in Astrophysics at Sheffield University. She decided that she wanted to inspire other young people, so moved to Bristol to complete a PGCE in Secondary Science. She particularly loves creating fun and absorbing materials to help students achieve their exam potential.