Understanding Scales and Scale Drawings

Understanding the concept of architectural Scales

You can download a handy pdf of this post Understanding Scale Drawings by clicking the download button below!

Scale drawings allow us to accurately represent sites, spaces, buildings and details to a smaller or more practical size than the original.

When a drawing is described as ‘to scale’, it means that each element in that drawing is in the same proportion, related to the real or proposed thing – it is smaller or indeed larger by a particular percentage.

If something is ‘drawn to scale’ we expect that it has been drawn, or printed, to a common scale that is used as standard in the construction industry. As we gain a better understanding of scale, we can view a drawing in a particular scale and instantly recognise and understand the spaces, zones and gain a quick understanding of the existing or proposed spatial relationships.

In the real world, one meter is equal to one meter.  A drawing at a scale of 1:10 means that the object is 10 times smaller than in real life scale 1:1. You could also say, 1 unit in the drawing is equal to 10 units in real life.

As the numbers in the scale get bigger, i.e. 1:50 – 1:200, the elements in the drawing actually get smaller. This is because in a drawing at 1:50 there is 1 unit for every 50 unit in real life. A drawing of 1:200 is representing 200 units for every one unit – and therefore is showing the elements smaller than the 1:50 drawing.

It is worth noting that scale drawings represent the same units. So, if a drawing is at 1:50 in cm, 1cm in the drawing will be equal to 50cm in real life. Similarly, if a drawing is in mm, at 1:200 – one mm unit in the drawing will represent 200mm in real life.

The image above shows an example of a drawing set with different scales to demonstrate different aspects of the design. (cad drawing courtesy of bibliocad.com). You may want to represent a site plan at a scale of 1:500, but show floor plans at 1:100 for example.

Working with scales for architectural representation

In architecture, we use a collection of standard scales to represent our designs. For example, it is common practice to produce floor plans at a scale of 1:100 (dependent on size of project and paper). Once you gain an understanding of scales, it is easy to understand which scale is most suited to which type of drawing.

Scale bar blocks courtesy of cad-blocks.co.uk. These scale bars show what one unit represents at different scales.

The general requirement of a scaled drawing is to convey the relevant information clearly with the required level of detail. If you are working in practice there will often be office standards. For example, they may only use layout sheets of either A3 or A1 – depending on the scale of the project and information that is being represented. As a student, you need to make these decisions based on industry standard. It is always best to use a ’round’ scale, i.e., one of the scales mentioned below, and not make up your own.

The following looks at the recommended scales for architectural use in the metric system. The chosen scale and paper size will often depend on the size of site/design of each individual project.


Site and Key Plans


Sketch schemes etc


Location / Plan drawings


Component / detail drawings

The following drawings show a project represented at different scales on an A3 page.

Working out the scale

A scale is shown as a ratio, for example 1:100. A drawing at a scale of 1:100 means that the object is 100 times smaller than in real life scale 1:1. You could also say, 1 unit in the drawing is equal to 100 units in real life.

So, if we were drawing a table that measured 100cm wide by 200cm long, at a scale of 1:50, you would draw the table 2cm wide by 4cm long on your piece of paper. This is worked out by dividing the real life size (100cm) by 50 (1:50 scale). This gives you a result of 2cm. For the length of the table we divide 200cm by 50 to get a result of 4cm.

Of course, it is not necessary to calculate the required measurements when you draw. You can either use a scale ruler to hand draw your plans, or software such as Revit, AutoCAD, ArchiCAD that will allow you to present your drawings at any scale and easily switch between scales as required.

How to use a scale ruler


A scale ruler is a tool that architects, engineers and designers use to draw their designs at an appropriate scale that it fits on a piece of paper and is in proportion to accurately convey the scheme. The scale ruler comes in different shapes, flat or triangular but they all provide sets

of graduated numbered spaces, that establishes a proportion of one unit to the specified unit, i.e. different scales. As an example, the ruler I have in front of me now has the following scales; 1:1, 1:100, 1:20, 1:200, 1:5, 1:500, 1:1250, 1:2500. 


Scale rules have varying number of scales on them, depending on their intended use. Using a scale rule is pretty easy when you know how. 


When you are drawing a plan, you select the scale you intend to use by turn the ruler to the appropriate side. You can then draw the line to the desired measurement using the scale ruler. For example, if you have select to draw a 5m wall at 1:100, you would select your 1:100 side of the ruler, and draw 5 units along the ruler, as each unit represents 1m. 

When you are reading plans, you establish the scale of the drawing or plans, and select that scale on your ruler, you are then able to measure the lines using the correct scale. 

Working with scales digitally

One of the great things about using digital drafting software is that you can produce drawings as multiple scales from one single drawing. Programs such as Revit, AutoCAD, ArchiCAD and many more, allow you to draw up your designs at 1:1 scale, that is real life size, and produce drawings or plots of these designs at an appropriate scale for the paper size you have selected. 
When working in CAD you can let the software do some of the hard work for you by making use of the paper space option to create layouts. On your layout sheet you are then able to create viewports which feature your drawing at the required scale. I have recorded a couple of tutorials that will help with setting up drawings for printing at appropriate scales.


I have also recorded a tutorial that explains how to scale a drawing in cad. This is useful if you have imported a drawing at a different scale.

You can download my dynamic scale bar cad blocks here:

You can download a handy pdf of this post by clicking the download button below!

 Hope you find this useful, if you have any questions, or there is something else you would like to know about, please drop me an emaill ([email protected]) or comment below 🙂

My favourite Tools and Resources

I have curated a list of some of the tools and resources I would strongly recommend for anyone studying or working in Architecture.