An architect's scale is a specialized ruler

Ruler

A ruler, sometimes called a rule or line gauge, is an instrument used in geometry, technical drawing, printing and engineering/building to measure distances and/or to rule straight lines...

 designed to facilitate the drafting and measuring of architectural drawing

Architectural drawing

An architectural drawing or architect's drawing is a technical drawing of a building that falls within the definition of architecture...

s, such as floor plan

Floor plan

In architecture and building engineering, a floor plan, or floorplan, is a diagram, usually to scale, showing a view from above of the relationships between rooms, spaces and other physical features at one level of a structure....

s and orthographic projections

Multiview orthographic projection

With multiview orthographic projections, up to six pictures of an object are produced, with each projection plane parallel to one of the coordinate axes of the object....

. Because the scale

Scale (ratio)

The scale ratio of some sort of model which represents an original proportionally is the ratio of a linear dimension of the model to the same dimension of the original. Examples include a 3-dimensional scale model of a building or the scale drawings of the elevations or plans of a building. In such...

 of such drawings are often smaller than life-size, an architect's scale features multiple units of length

Unit of length

Many different units of length have been used across the world. The main units in modern use are U.S. customary units in the United States and the Metric system elsewhere. British Imperial units are still used for some purposes in the United Kingdom and some other countries...

 and proportional length increments.

For accuracy and longevity, the material used should be dimensionally stable and durable

Durable

Durability is the ability to endure. It can refer to:*Durable goods, goods with a long usable life in economics.*Durability , one of the ACID properties.In safety and technology:*Dust resistant*Fire resistant*Rot-proof...

. Scales were traditionally made of wood, but today they are usually made of rigid plastic

Plastic

A plastic material is any of a wide range of synthetic or semi-synthetic organic solids used in the manufacture of industrial products. Plastics are typically polymers of high molecular mass, and may contain other substances to improve performance and/or reduce production costs...

 or aluminium

Aluminium

Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....

. Architect's scales may be flat, with 4 scales, or have a symmetric 3-lobed cross-section, with 12 scales.

United States and Imperial units

In the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, and prior to metrification

Metrication

Metrication refers to the introduction and use of the SI metric system, the international standard for physical measurements. This has involved a long process of independent and systematic conversions of countries from various local systems of weights and measures. Metrication began in France in...

 in Britain

United Kingdom

The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

, Canada

Canada

Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

 and Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

, architect's scales are/were marked as a ratio of x inch

Inch

An inch is the name of a unit of length in a number of different systems, including Imperial units, and United States customary units. There are 36 inches in a yard and 12 inches in a foot...

es-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). It is not to be confused with a true unitless ratio (inches to inches)-- a 1:50 architectural scale would be a 1:60 unitless scale.

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 (one scale is read from the right, and the other scale is read from the left):

• three-inches-to-the-foot (3"=1'-0") (ratio equivalent 1:4)/one-and-one-half-inch-to-the-foot (1½"=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)

Metric units

Architect's scale rulers used in Britain and other metric

Metric system

The metric system is an international decimalised system of measurement. France was first to adopt a metric system, in 1799, and a metric system is now the official system of measurement, used in almost every country in the world...

 countries are marked with ratio

Ratio

In mathematics, a ratio is a relationship between two numbers of the same kind , usually expressed as "a to b" or a:b, sometimes expressed arithmetically as a dimensionless quotient of the two which explicitly indicates how many times the first number contains the second In mathematics, a ratio is...

s without reference to a base unit. Therefore a drawing will indicate both its scale (ratio) and the unit of measurement being used.

In Britain, and elsewhere, the standard units used on architectural drawings are the (SI) units

International System of Units

The International System of Units is the modern form of the metric system and is generally a system of units of measurement devised around seven base units and the convenience of the number ten. The older metric system included several groups of units...

 millimetre

Millimetre

The millimetre is a unit of length in the metric system, equal to one thousandth of a metre, which is the SI base unit of length....

s (mm) and metre

Metre

The metre , symbol m, is the base unit of length in the International System of Units . Originally intended to be one ten-millionth of the distance from the Earth's equator to the North Pole , its definition has been periodically refined to reflect growing knowledge of metrology...

s (m), whereas in France centimetre

Centimetre

A centimetre is a unit of length in the metric system, equal to one hundredth of a metre, which is the SI base unit of length. Centi is the SI prefix for a factor of . Hence a centimetre can be written as or — meaning or respectively...

s (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

• 1:10/1:100

• 1:20/1:200

• 1:1250/1:2500

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

Less common scales are:

• 1:25/1:250

• 1:33

External links

• Engineering and Architectural Scale Information.