7: Antilogs

If you know the value of a number on the log scale and you want to find the original value of the number, how do you find it?

Use the antilog, of course!! The anti-logarithm (antilog) is the number corresponding to a given log, for example, the log of 1000 is 3, thus 1000 is the anti-log of 3. To get the antilog on your calculator, you can raise 10 to the log, or use the 10x key.

For example, suppose the log of a pollen diameter (measured in metres) was −4.5, then the diameter in metres is:

10−4.5 ≈ 0.0000316 m

 Note, 0.0000316 = 3.16 x 10 -5 m or 31.6 µm

If you are using Google as a calculator, type “10^−4.5 = ” and hit ENTER.

How big is a fly’s eye? The log of the diameter is −3.1…