Architect's scale
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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.
[edit] 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 (typically written as x"=1'-0"). 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 (3"=1'-0") (ratio equivalent 1:4) / one-and-one-half-inch-to-the-foot (1-1/2"=1'-0") (1:8)
- one-inch-to-the-foot (1"=1'-0") (1:12) / one-half-inch-to-the-foot (1/2"=1'-0") (1:24)
- three-quarters-inch-to-the-foot (3/4"=1'-0") (1:16) / three-eighths-inch-to-the-foot (3/8"=1'-0") (1:32)
- one-quarter-inch-to-the-foot (1/4"=1'-0") (1:48) / one-eighth-inch-to-the-foot (1/8"=1'-0") (1:96)
- three-sixteenths-inch-to-the-foot (3/16"=1'-0") (1:64) / three-thirty-seconds-inch-to-the-foot (3/32"=1'0") (1:128)
[edit] 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
One example is the Design Line 81-1704, made in Japan. Its measuring range is 15 centimetres, and it employs the American decimal point once, at the end point of the 1:50 scale at 7.5m. For scale at or below 1:20, it reads mm at the first number after zero and at the end; for scales above 1:20, it reads m.
For triangular rulers, the paired scales are:
- 1:1 / 1:10
- 1:2 / 1:20
- 1:5 / 1:50
- 1:100 / 1:200
- 1:500 / 1:1000
- 1:1250 / 1:2500
The scale will have a long mark to the left of a zero, which is the beginning of the feet, and several shorter marks to the right of the zero, which represents the inches. Line up the zero mark with the beginning of the section you want to measure. The nearest mark the line passes, is the foot measurement. Often, since the same side will have two scales on it, the marks will alternate one scale and then the other, even to odd. You must make sure you know which one you should be using. Once you count up the feet, slide the ruler left to meet up the end of the line with the nearest foot mark. The beginning of the line will bleed over the zero mark to the right. The shorter 'inch' mark that the line meets up with, will be the amount of inches you need. The first measurement gives you the feet, the second the inches. No math involved, and after a bit of practice, it will become second nature.
