Expert: Walter Hintz - 9/26/2007

Question
QUESTION: Please can you explain how to calculate surface area to volume ratio and give an example for me to follow!

Thank you ^__^

ANSWER: Hi Yaz
Lets do some simple math
 Assume a cube with a side of 1 cm
  Surface area of a cube = 1x1 x 6 (six sides) is 6 square cm
  Volume of a cube = 1x1x1= 1 cubic cm
 Ratio is 6 to 1
 Now consider a cube with a side of 2 cm.  make the calculations and get back to me so I know you understand.

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QUESTION: Answer:
Surface area of a cube= 2x2x6= 24 square cm
Volume= 2x2x2=8 cubic cm
Ratio is 24 to 8 or 3 to 1

I've worked this out by looking at the example you gave, but i don't understand how you got the volume 1x1x1. What does it represent?

Thank you

ANSWER:   You did it correctly
The formula for the volume of a rectangle or a cube is length x width x heighth  (V=lwh)  Since all sides of a cube are equal the formula would be the edge (or side) cubed or 1x1x1

You will notice taht as the sise of the cube increases the ratio decreases.  This is called the scale effect

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QUESTION: Thanks for your help. So to be clear in my mind, with a cube with a side of 4cm.....
Surface area of the cube: 4x4x6=96 square cm
Volume: 4x4x4=64
Ratio: 96 to 64 or 1.5 to 1

Answer
 Correct
Let me give you one more example
If we use a side of 10 cm
 SA  is 10 x  10 x 6 = 6000 sq cm
 Vol is 10 x10 x10   = 10000 cu cm
ratio is 0.6 to 1

  Are you asking about this in relation to cell size and if so do see the relevance as to why cells are small?