How To Use An Architectural Scale Ruler (Metric) - ArchiMash.com (2024)

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A Scale What?

When you start architecture school you will hear people talk about scale and scale rulers. Most of the time they will assume you know what this is and won’t tell you how to use an architectural scale ruler.

You might spend weeks not knowing what a scale ruler is and even if you do, what the heck you’re supposed to do with it. The thing is, it’s one of the most critical drawing tools you’re going to use.

Before we consider a scale ruler, it might be helpful to understand a little bit about scale.

What Is Scale?

Scale in design refers to the enlarged or reduced representation of a real, full-size object in a drawing or physical model while retaining the proportions of the original. In architecture, we generally reduce the scale rather than enlarge it. A scale drawing or model is like taking the original and shrinking it down proportionally.

We can either work in metric (metres, centimetres, millimetres) and imperial (feet and inches).

It is important to note that architects generally use millimetres when developing their drawings, not centimetres or metres.

With metric scale, we pronounce scale as “one” which is the number on the left, “is to” which is the colon “fifty” which is the number on the right.

• The number on the left of the colon refers to one unit on the page as a representation of real life.
• The number on the right of the colon refers to how many time larger the real-life measurement is.

For example, a scale of “one to twenty” means that one millimetre on a page represents twenty millimetres in real life.

What is important to note is that when a single line or length is drawn on a page the real-life line is twenty times longer.

When a square or an area (length x width) is drawn on a page, the real-life area is twenty times the length and twenty times the width, so 400 times larger.

When a mass or a volume (length x width x height) is either drawn three-dimensionally or created as a physical model, the real-life volume is twenty times the length and twenty times the width and twenty times the height, so 8,000 times larger.

Types Of Scale

Certain scales are used to produce different drawings. These include:

Learn more in the article titled “An Introduction To Architectural Drawing Systems”

Choosing A Scale Ruler

A scale ruler is used to help understand the proportions of the drawing or model representation as a proportion of the real-life object.

The first thing you must consider in choosing a scale ruler is which type of unit of measurements you are using. This will vary depending on which country you reside in.

• Imperial Units – Refer to feet and inches.
• Metric Units – Refer to millimetres (mm), centimetres (cm) and metres (m).

The second consideration in choosing a scale ruler is which scales you will be using. This will depend largely on your profession or discipline.

• Engineering Scales include scales such as 1:75, 1:300, 1:400
• Urban Scales might include just large scales such as 1:10,000, 1:20,000
• Architectural Scales include scales such as 1:1, 1:2, 1:5, 1:10, 1:20, 1:50, 1:100, 1:200, 1:500 and more rarely 1:25 or 1:250.

As an architecture student, you should use the standard scales in the presentation of your work and avoid unusual scales such as 1:75,1:300, or 1:400.

Using A Scale Ruler

Once you have the correct scale ruler, how do you use it? There are two ways to use a scale ruler:

• Converting measurements from real life to a scale drawing; and
• Converting measurements on a scale drawing to real life.

01 | Convert Real Life To A Scale Drawing

To create a drawing from a real-life object we first determine the scale we are using for that particular drawing. Say we are drawing a bathroom room layout at 1:50 (one is to 50).

We measure the bathroom in millimetres. Say it is 3,600mm x 2,400mm (3.6m x 2.4m).

We can try to convert from 3,600mm by dividing by 50, or we can use a scale ruler.

• We take our scale ruler and flip it to our 1:50 scale.
• We can see that 1000mm (or 1.0m) in real life is equivalent to 20mm (or 2cm) on our scale ruler.
• We can see that 3,600mm in real life is equivalent to 72mm on our scale ruler.

You can see how all this swapping between metres, centimetre and millimetres is confusing so we use millimetres.

If you are drawing with a computer-aided drawing (CAD) program you will be drawing at 1:1 and then representing your scale on a page. However, in the early stages of design, it is important to start developing your ideas with old fashioned pencil, pen and paper. During this stage, you should have a scale ruler in your hands so that you are thinking about the measurement of something in real life and can immediately draw it to scale on the page. You do not have to keep converting real-life numbers to your scale in your head, and therefore reduce the risk of error.

Learn more in the article titled “Plan Section And Elevation In Architecture For Beginners”

02 | Convert A Scale Drawing To Real Life

The other way we can use a scale ruler is to convert the measurements on a drawing to real life. The first thing we must check is that a drawing has been printed at the correct scale. If not, we must determine the scale within the drawing.

Once we know the drawing scale, we can use a scale ruler to determine the measurement shown on the drawing in real life. Say your drawing is a floor plan at 1:100 and we want to know how big the internal bathroom is.

• We take our scale ruler and flip it to our 1:100 scale.
• When we measure the internal walls of the bathroom we can see that the drawing is 36mm x 24mm.
• Our scale ruler tells us these measurements are 3600mm (3.6m) x 2400mm (2.4m) in real life.

Representing Scale

Before we start a drawing we must choose our scale and use it consistently. We must also clearly indicate the scale on the drawing so our viewer knows how to measure. There are three ways to represent a scale on a drawing.

• Human Body – Showing a human body on a drawing immediately gives the reader an indication of the scale. This is more commonly used in the concept, schematic and design development drawings, and NOT construction or working drawings.
• Written Scale – Within each drawing title on a drawing page or sheet you can include the scale of that drawing or detail. This is written as “1:20 on A3” or “1:100 on A1.” This is fine if you know the drawing has been printed to scale but if for example, an A3 drawing is printed on A4, there is no way of knowing the correct scale. When we know the scale of the drawing is correct, we can use a scale ruler.
• Scale Bar – These are shown on a drawing and represent a printed scale like the scale on a scale ruler. They immediately allow the reader to compare the scale within the drawing to a defined scale on the scale bar. The great thing about scale bars is they adjust automatically and proportionally when a drawing page is shrunk or enlarged. We can use a scale bar like a scale ruler when the drawing has been printed to an unusual scale.

Converting Between Scales

One of the trickiest things is converting between scales. For example, you may be asked to convert a 1:500 site plan to a 1:100 floor plan, or a 1:100 elevation to a 1:10 detail. Sometimes the maths is easy enough.

If not, I have created a simple “Drawing Scale Conversion Sheet” that allows you to simply and easily convert between scales.

Most of the time, you should be able to use your scale ruler.

What Next?

CAD software programs are great, and while you are designing and documenting you may come to rely on these a lot. This means you will be thinking at a scale of 1:1.

However, the minute your drawings are printed to scale on a page, you need to be able to read and interpret them.

You will also need to be able to use a scale ruler when sitting face-to-face with anyone to develop concepts and design and discuss your work. This will include working with your tutors, clients, your boss, other consultants, or builders or tradespeople on a building site.

You will not have the opportunity to go back to your computer to open up our software and check the measurements. You need to be able to recognise what things look like on paper at different scales.

Your scale ruler is one of the most useful tools of your trade. You must start learning to use it now!!

Until next time…

…Liz at ArchiMash