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Architect's Scale

An architect's scale is a ruler marked for reading measurements off drawings made at standard imperial scales, such as 1/4 inch equals 1 foot. It lets a reader measure a line on a plan and read the real length directly in feet and inches.

The most familiar version is a three-sided triangular ruler, with a different scale along each edge and one scale reading from each end. Common residential scales are 1/4 inch = 1 foot (a ratio of 1:48) and 1/8 inch = 1 foot (1:96). An engineer's scale is a similar tool divided into tenths for site and civil drawings.

An architect's scale only gives correct readings on a drawing printed at its original size. See drawing scales.