A logarithmic scale is a scale of measurement that uses the logarithm of a physical quantity instead of the quantity itself.

Presentation of data on a logarithmic scale can be helpful when the data covers a large range of values - the logarithm reduces this to a more manageable range. Some of our senses operate in a logarithmic fashion (Weber–Fechner law), which makes logarithmic scales for these input quantities especially appropriate. In particular our sense of hearing perceives equal ratios of frequencies as equal differences in pitch.