Size of Cells

• The sizes of plant , animal and prokaryotic cells

  • A typical plant cell may be about 0.1 mm in diameter
  • A typical animal cell may be about 0.2 mm in diameter 
  • Prokaryotic cells are smaller - often about 0.002 mm in diameter
• Number of units in 1 metre (This basically means , if we were to split 1 metre into a certain number of equal pieces , than we would end up with a different unit of measurement)

  • Centimetre (cm) - 100 units in 1 metre  
  • Millimetre (mm) - 1000 units in 1 metre 
  • Micrometre (µm) - 1,000,000  units in 1 metre 
  • Nanometre (nm) - 1,000,000,000 units in 1 metre
• Units of measurement as a fraction of a metre 


  • Centimetre (cm) - 1/100ᵗʰ of a metre 
  • Millimetre (mm) - 1/1000ᵗʰ of a metre
  • Micrometre (µm) - 1/1,000,000ᵗʰ of a metre
  • Nanometre (nm) - 1/1,000,000,000ᵗʰ of a metre
• Different units of measurement written as metres (m) in standard form

  • 1 Centimetre (cm) = 1 x 10⁻² m
  • 1 Millimetre (mm) = 1 x 10⁻³ m
  • 1 Micrometre (µm) = 1 x 10⁻⁶ m
  • 1 Nanometre (nm) = 1 x 10-9 m
• 1 metre written as different units of measurement in standard form

  • 1 m = 1 x 10² cm (centimetres)
  • 1 m = 1 x 10³ mm (millimetres) 
  • 1 m = 1 x 10⁶ µm (micrometres) 
  • 1 m = 1 x 10⁹ nm (nanometres)
• Sizes of other things that you may or may not need to know

  • The average length of a dog like a German shepherd is around 1m 
  • The width of your little finger is around 1cm 
  • The tip of a ball point pen is around 1mm 
  • A typical human cell is around 10-20 µm 
  • The diameter of a haemoglobin molecule is around 5 nm