Architectural Scale Guide

Architectural drawing scales and scaled drawings can be a difficult subject to understand, especially for new students...
Architectural Scale Guide

Architectural drawing scales and scaled drawings can be a difficult subject to understand, especially for new students (and even clients) that have not experienced them or had the need to use them before.

Scale is important because it enables us to recognize the relationship between a drawing or physical model and the reality of its real world size. 

For this reason learning how to read and use drawing scales (whether digital or analog) forms a fundamental and core skill that every architecture student must adopt at the very early stages of their architectural education (if not before).

…As due to the general size of architecture projects, it is only on very rare occasions that an architectural drawing is not shown and drawn in an architectural scale.

Producing accurate scaled drawings at varied scales, is one of the most important aspects of architectural drawing and spatial design.


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Drawing scale definition

In short, a drawing scale allows real objects and/or subjects to be accurately represented at fixed reduced and enlarged sizes, which can then be measured via a scale rule to determine their real world size.

Scale drawings definition 

Scale drawings are defined as a document that contains and represents a scaled object and/or subject.

It can be produced on any paper format and size, with the scale clearly annotated and often accompanied by a scale bar.

The architects scale 

As architects and architectural students, whether you work with metric of imperial units, there are set scales that are used to produce scale drawings, and these are:

Architectural scales metric 

  • 1:5000 – Pronounced one to five thousand
  • 1:1000
  • 1:500
  • 1:200
  • 1:100
  • 1:200
  • 1:100
  • 1:50
  • 1:20
  • 1:10
  • 1:5

Architectural scales imperial 

  • 3″=1′-0″ – Pronounced three inches to a foot
  • 1 1⁄2″=1′-0″
  • 1″=1′-0″
  • 1⁄2″=1′-0″
  • (3⁄4″=1′-0″)
  • (3⁄8″=1′-0″)
  • (1⁄4″=1′-0″)
  • (1⁄8″=1′-0″)
  • (3⁄16″=1′-0″)
  • (3⁄32″=1′0″)

It’s very unusual for a scaled drawing to deviate away from using one of these set scales, and as architecture students you should always aim use these standards.

Custom scales tend to show inexperience, and must be accompanied by a scale bar, which is both unsightly and adds an unnecessary layer of complication to presentation drawings.

We discuss how to choose a scale further on in this article…

How to read scale drawings

You may have heard the common term ‘to scale’, which for those that don’t know simply means that every component within a drawing or physical model is in the same proportion to one another, and is represented by one of the above common scales.

When reading a scaled drawing, the scale is shown as the length in the drawing, then a colon (“:”), and then the matching length on the real object. 

For example, a floor plan of a building drawn using a metric scale of 1:100 (pronounced “one to a one hundred”), means that for each unit that is measured on the drawing (the 1), the real world size of it is 100 times larger (the 100) than it appears.

 So if a measurement taken from the drawing is 10mm, then at real world scale would be 1000mm when built.

With this in mind, a 1:1 (“one to one”) scale is the real world scale of everything, and the scale that we draw and 3D model in when using CAD and 3D programs (…more on this below). Anything can be scaled correctly however through using the CAD scale factors discussed here.

The below and slightly cheesy video further demonstrates how to read an imperial scale:

Producing a scaled drawing

As mentioned above, scale is used in architecture as a tool to represent large objects at a smaller size in order to allow them to be read with ease on a standard sized sheet of paper.

When producing these drawings by hand, the scale of floor plan or elevation for example must be chosen and drawn in that scale.

However today, most if not all drawings are produced via CAD and 3D programs and always drawn at a real world size (known as 1:1), meaning that in your chosen CAD program 1000mm will equal 1000mm, or 1ft will equal 1ft when measured. You draw it as if you were building it.

The reason for this is so that when it comes to printing/plotting your drawings, you can choose the scale you want to suit the type and size of the drawing you want to produce.

This means that the same floor plan could you shown at 1:100 for say a presentation, and then parts of it could be shown at 1:10 to show the detail and make-up of the wall construction.

Choosing a scale

The chose of scale is determined by the type of drawing, the size of the subject and the size of paper or document that you wish to present it on.

For example a construction detail of a wall junction needs to be a much larger scale than a general section of the whole building. The wall detail might have a scale of 1:10 or 1:5, whereas the general section is likely to be 1:50 (in metric units)

This is firstly because as they are communicating different aspects and situations of the building; the detail needs to show only one small part of the building, but in a great amount of detail.

..And the section needs to show the general arrangement of whole building, which requires a much larger part of the building but in much less detail.  

If they both had the same scales then one would either be too small of too large, when presented on a sheet.


Types of metric and imperial scale drawings 

As mentioned above, the type of scale you choose is dependent of the type of drawing you wish to produce.

The below list provides a guide for the metric and imperial scales that we suggest are used for the most common architectural drawings:

Standard scales for architectural drawings 

1:5000 – Location plan

1:1000 (1”=80’0”) – Location Plan

1:500 (1”=40’0”) – Site plan

1:250 (1”=20’0”) – Site plan (note that 1:250 is not a common metric scale)

1:200 (1/16”=1’0”) – Site plan

1:100 (1/8”=1’0”) – Floor plans, elevations and sections

1:50 (1/4”=1’0”) – Floor plans, elevations and sections

1:25 (3/4”=1’0”) – Room plans, interior elevations (note that 1:25 is not a common metric scale)

1:20 (3/4”=1’0”) – Room plans, interior elevations

1:10 (1 1/2”=1’0”) – Joinery, component details, construction details

1:5 (3”= 1’0”) – Construction details

1:2 (Half size) – Construction details

1:1 (Full size) – Construction details

Working out a scale

When wanting to work out the scale of a drawing, there should be a clear indication of it either next to the drawing, in the drawings title block or on a scale bar.

Failing that and if the drawing has dimensions, then a scale rule can be used with a little trial and error to find the correct scale.

Measuring scale

The architects scale ruler 

The most common method of measuring a scaled drawing is via a scale rule, and we have a list of our favorite and most versatile rules here.

Initially, how to use a scale rule to measure drawings may seem overwhelming, and it’s also very likely that you will require more than one rule, as different rules have different scales.

That aside and once you have identified that you have the right scale rule and scale units, then measuring a drawing is no different to measuring and using a standard ruler. Simply take the measurement and record it.

Our favorite imperial scale rule is the 12″ Black Aluminum Triangular Scale Rule by Alvin, it provides scales in 3/32 3/16 3/4 3/8 3 1 1/2 1/8 1/4 1/2 1 inch, and due to its aluminum construction is has a very nice sturdy and substantial feel to it when compared to other plastic versions.

For metric scale rules, we highly recommend the Bocianelli range of Triangular Scale Rules, which similar to the above, are also an aluminum construction and last forever!

Scale bars

A second and slightly less precise method of measuring a drawing is via a scale bar (examples below). These effectively represent a printed scale rule, and therefore their measurement can be taken and translated to just about any measuring device that might be to hand.

…even a plain piece of paper can be transformed into a rule by marking on the scale bars units and moving the edge of the paper around the drawing to take measurements. 

Architectural scale checklist

  • Have you chosen the right scales for the right drawings?
  • There is no one size fits all, and you should communicate your project with a range of scales.
  • Can you read between drawings and their scales easily? Some drawing such as plans and elevations may read better if they are same scale and presented next to each other.
  • As mentioned above, architects and designers use ‘common’ scales, and you should not deviate away from these. Use the drawing and scale guide above
  • Are your drawings clearing labelled with the correct scale? Do you need a scale bar?
  • Does the detail within your scaled drawing justify the scale it is shown in? Should you reduce or increase the scale, or add more detail to the drawing as a whole?
  • Your chosen scale should be within proportion to your paper size.
  • Working out and measuring scale is easy with a scale rule
  • Populate your drawing with people, trees, furniture and vehicles to further provide scale and spatial awareness.
  • CAD programs scale and show how your drawings will fit on your chosen paper size …let the computer do the hard work.
  • When using CAD and 3D software, always draw and model in 1:1.
  • When printing/plotting your work, do not select “scale to fit”.


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This Post Has 4 Comments

  1. Jake

    Your imperial scaling is incorrect. 3″=1′-0″ is 1:4 not 1:5, and 1-1/2″=1′-0″ is 1:8 not 1:10.

    1. archisoup

      Hi Jake,

      Yes very true, and thank you for flagging this up …what we are showing here however is how standard Imperial scales convert to the closest standard Metric scale (perhaps we could make this clearer though).

      The actual conversions of 1:4 and 1:8 for example, do not tend to feature on a scale rule.


  2. JJAB

    Is there any generic software that can be used for digital documents that will allow you to measure/change the scale

    1. Kaz

      Give SketchUp a try. You can draw a model at full scale in whatever system is comfortable to you and then just change the units of measure and SketchUp will do all of the math and the measurements will appear correctly in the desired units. For instance, if you draw a 30mm x 30mm square and measure it, it will measure 30mm x 30mm. Change the units of measure to English and measure again and the square will measure 1.1811″ x 1.1811″.

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