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Drawing Scale

A drawing scale is the fixed ratio between a length on a drawing and the matching length in the real world. It is written either as an equation, such as 1/4" = 1'-0", or as a ratio, such as 1:48 or 1:100.

Imperial plans usually use architectural scales like 1/4 inch or 1/8 inch to the foot. Metric plans use ratios such as 1:50 or 1:100. A scale bar, a short ruler printed on the sheet, stays accurate even when the drawing is enlarged or reduced, which a written scale does not.

Every length measured from a plan depends on the scale being right. Setting it from one known dimension is more reliable than trusting the printed note. See floor plan scale explained and drawing scales.