A scale is both a device used for measurement of weights, and a series of ratios against which different measurements can be compared. The latter need not always be a linear ratio, and is often logarithmic.
A draughtsman's scale refers to a ruler-like device, often with a triangular cross-section, that permits him to represent items in the same relative dimensions.
The scale of a map or enlarged or reduced model indicates the ratio between the distances on the map or model and the corresponding distances in reality or the original. E.g. a map of scale 1:50,000 shows a distance of 1 km as 2 cm, and a model on a scale 1:25 of a building with a height of 30 m has a height of 1.20 m. In model railways a number of standard scales are indicated by letters such as "G", "O", "HO", "N" and "Z".
Scales with special uses are often named after the person who invented them.
- The Richter Scale, the Mercali Scale, the Rossi-Forel Scale and the Omori are all used to measure the intensity of earthquakes.
- The Beaufort scale is used to measure wind force.
- The Goldberg scale measures mania and depression.
- The Scoville Scale measures the hotness of peppers