An architect scale is a specialized ruler used in architectural drawing to make and read scaled representations of buildings and structures. Unlike mechanical or engineer’s scales, which use direct ratios, an architect’s scale is based on inch-to-foot relationships. This means the drawing is still in inches, but each marked unit on the scale represents a full foot in real life.
The physical instrument is often a triangular scale with six edges, each edge carrying two different scales, for a total of twelve scales. Common ones include 1/4 inch = 1 foot, 1/8 inch = 1 foot, 1/2 inch = 1 foot, and so on. For instance, if a drawing is made at 1/4 inch = 1 foot, then every quarter-inch on the page equals one real-world foot. On that edge of the scale, the numbers read as feet, not inches, so you can measure directly from the drawing without performing conversions.
Beyond the zero point, there is often a short segment subdivided into divisions representing inches. These smaller divisions allow precise measurement of inches within each foot, since architectural drawings commonly represent dimensions in feet and inches, not decimals.