Drafting Scale Rulers Read Architectural & Engineering Drawings in Inch & Metric

Scale - In drafting, architecture and engineering the term scale has two meanings. A scale is a dimension that represents the structure shown in a plan. A scale is also a ruler used in drawing and measuring architectural and engineering plans.

Architectural scales units are based on foot/inch dimensions. Floor plan drawings are usually drawn to the scale of 1/4" = 1'-0". For a very large plan, a scale of 1/8" = 1'-0" may be used. When drawing a small plan or a single room, scales of 3/8" = 1'-0", 1/2" = 1'-0", 3/4" = 1'-0", or 1" = 1'-0" may be used to fit the size of your drawing format.

Engineers Engineering Scales units of measure are equal to parts per inch and parts per foot. The most common graduations are 10, 20, 30, 40, 50, 60 parts per inch, but there are scales available that have 100, 200, 300, 400, 500, 600 parts per foot. The graduations vary based on the application.

Metric Engineering Scales - metric scale measurements is the standard in most of the world. The principles are similar. You have to get used to measurements expressed in meters (m) and millimeters (mm). One meter is slightly larger than one yard. A millimeter is 1/1000 of a meter. Metric scales are usually based on ratios. A ratio is the relationship of one measurement to another. For example, metric plot plans are often drafted in ratios of 1:100. This scale is very close to the scale 1/8" = 1'-0" (1:96). Metric floor plans are drawn in a ratio of 1:50. This is very close to a scale of 1/4" = 1'-0" (1:48). Construction details may be drawn to metric scales of 1:20, 1:10, or 1:5. It should be noted that all dimensions in metric dimensions are in millimeters. Therefore, it is not necessary to use the symbol mm.