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An architect's scale is a specialized ruler. It is used in making or measuring from reduced scale drawings, such as blueprints. It is marked with a range of calibrated scales (ratios).
The scale was traditionally made of wood but for accuracy and longevity the material used should be dimensionally stable and durable. Today they are now more commonly made of rigid plastic or aluminum. Depending on the number of different scales to be accommodated architect's scales may be flat or shaped with a cross-section of an equilateral triangle.
United States and Imperial units
In the United States, and prior to metrification in Britain, Canada and Australia, architect's scales are/were marked as a ratio of x inches-to-the-foot. For example one inch measured from a drawing with a scale of "one-inch-to-the-foot" is equivalent to one foot in the real world (a scale of 1:12) whereas one inch measured from a drawing with a scale of "two-inches-to-the-foot" is equivalent to six inches in the real world (a scale of 1:6).
Typical scales used in the United States are:
- Full scale, with inches divided into sixteenths of an inch
The following scales are generally grouped in pairs using the same dual-numbered index line:
- three-inches-to-the-foot (1:4) / one-and-one-half-inch-to-the-foot (1:8)
- two-inches-to-the-foot (1:6) / one-inch-to-the-foot (1:12)
- three-quarters-inch-to-the-foot (1:16) / three-eighths-inch-to-the-foot (1:32)
- one-half-inch-to-the-foot (1:24) / one-quarter-inch-to-the-foot (1:48)
- one-eighths-inch-to-the-foot (1:96) / one-sixteenths-inch-to-the-foot (1:192)
Metric units
Architect's scale rulers used in Britain and other metric areas are marked with ratios without reference to a base unit. Therefore a drawing will indicate both its scale and the unit of measurement being used.
In Britain the standard units used on architectural drawings are the SI units millimetres (mm) and metres (m), whereas in France centimetres (cm) and metres are most often used.
In Britain, for flat rulers, the paired scales often found on architect's scales are:
- 1:1 / 1:100
- 1:5 / 1:50
- 1:20 / 1:200
- 1:1250 / 1:2500
and for triangular rulers:
- 1:1 / 1:10
- 1:2 / 1:20
- 1:5 / 1:50
- 1:100 / 1:200
- 1:500 / 1:1000
- 1:1250 / 1:2500
See also
"Architect's scale"