Architectural scale

Architectural scale is essential for creating accurate drawings and models in architecture. It allows life-sized objects to be precisely reduced onto paper. This helps architects and architecture students communicate their designs effectively, taking into account users, surroundings, materials, and structure. Builders then use these scaled drawings to construct the designs accurately.

What is architectural scale?

Architectural scale involves shrinking real-life objects, such as a city or building, proportionally for a drawing or model. It is expressed as a ratio, like 1:100, which shows how much smaller the object is.

For instance, in a 1:100 scale drawing, 1mm on the drawing represents 100mm in real life, making it 100 times smaller. The phrase ‘to scale’ means the drawing adheres to these proportions.

Understanding architectural scale is crucial for accurately representing spaces, buildings, and components, whether working on a city plan or a piece of furniture.

Architectural scale list

Standard scales are well-known and widely understood within the industry. It’s important to avoid choosing random scales and instead stick to standard architectural scales. With experience, you'll be able to look at a drawing and accurately guess its scale. Since scale is a key language in architecture, avoid creating your own ‘words,’ as others may not understand them.

For architectural design, the metric system is used in nearly all countries outside the US. The US, however, continues to use the imperial system, while countries like Canada, Pakistan, and India use both imperial and metric systems.

Metric architectural scales

A table showing metric drawing scales and their uses

Architects use millimetres (mm) and metres (m), but not centimetres (cm).

The colon ‘:’ in a scale is pronounced ‘to,’ so 1:100 is spoken as ‘one to one hundred.’

While scales like 1:25, 1:30, and 1:250 may appear, it’s standard practice to use 1:20, 1:50, and 1:200 instead.

A helpful way to remember these common scales is by associating them with coins: 1p/1c, 2p/2c, 5p/5c, 10p/10c, 20p/20c, 50p/50c, £1/€1, and £2/€2.

Imperial architectural scales

A table showing imperial scales and their uses

Some architects use feet and inches.

The equals sign ‘=’ is pronounced ‘to,’ so 3″=1′0″ is spoken as ‘three inches to a foot.’

How to use architectural scales

Select a scale

When choosing a scale for your drawing, remember that the larger the number after '1:' in the scale, the smaller the drawing will be. For example, a house drawn at a 1:500 scale will appear much smaller on paper than one drawn at a 1:100 scale.

Consider the following when selecting a scale

Size of the real-life object: Larger objects or projects may require smaller scales (e.g., 1:500).
Level of detail required: More detailed drawings, like floor plans, generally require larger scales (e.g., 1:100).
Paper size you are using: Ensure the scale you choose allows the drawing to fit well on the paper size you plan to use.
Stage of the design process: Early-stage designs may use smaller scales for broad overviews, while detailed designs use larger scales.

Calculate a scale-factor

To convert real-life measurements to drawing measurements, you can calculate a scale factor.

With a 1:100 scale, everything in the drawing is 100 times smaller than in real life. The scale factor is 0.01 (calculated as 1/100 = 0.01).

For a 1:50 scale, the factor is 0.02 (calculated as 1/50 = 0.02).

To apply the scale factor

Multiply the real-life dimension by the scale factor.

For example, in a 1:100 drawing, 1000mm in real life would be represented as 10mm (1000 x 0.01 = 10).

In a 1:50 drawing, an 8m wall in real life would be represented as 160mm on the drawing (8000mm x 0.02 = 160mm).

Scale in 2D and 3D

At 1:10 scale everything is 10 times smaller, which is true for a single line.

However, when you draw a square, the area (length x width) is reduced by 10 times in both dimensions, making it 10 x 10 = 100 times smaller in area.

This concept extends to three-dimensional volumes, where a cube's volume (length x width x height) would be reduced by 10 x 10 x 10, making it 1,000 times smaller.

Convert between architectural scales

‍Scaling down means reducing the size of something by a specific scale.
Scaling up means increasing the size of something by a specific scale.

For instance, you might scale down the measurements of a house so that your drawing fits on a piece of paper, but scale up the design of a wedding ring to show details larger than real life.

Converting between scales, like moving from a 1:1250 site plan to a 1:100 floor plan, can be tricky without a conversion chart to guide you.

Table showing conversions between scales

Level of detail (LOD)

A common mistake in architectural scale drawings is including too much detail at a given scale. This often occurs when 3D models are converted into 2D drawings. For example, CAD software might allow you to draw every bolt and fixture, but if the final drawing is displayed at 1:100, these details will not be visible and may clutter the drawing.

Scale in CAD drawings

When working in CAD, always draw at a 1:1 scale.

You don't need to manually convert real-life dimensions to scale because CAD programs can output a PDF in your chosen scale automatically.

However, CAD software does not automatically adjust the level of detail based on the scale you choose. Therefore, even though you draw at 1:1, it’s crucial to be mindful of the scale at which the drawing will be printed or viewed, and adjust the level of detail in your drawings accordingly.

The importance of scale in architecture

Scales in architecture are more than just numerical ratios; they carry significant meaning. When drawing, it’s crucial to choose a specific scale with purpose, as the information conveyed at 1:100 differs from that at 1:500. Each scale corresponds to a different level of detail and stage in the project. By scaling down the real world, architects can effectively manipulate and rationalise information, focusing only on what's necessary. For example, at a 1:1000 scale, less detail is shown because it's not needed, avoiding unnecessary distractions.

When creating sets of drawings, such as plans, sections, and elevations, it’s important to maintain consistent scales across these documents so they can be easily compared and understood together.

Scale in the design process

Scale is not meant to complicate the design process; rather, it supports and enhances it. The design process is a journey that requires a thoughtful progression from broad concepts to detailed plans. For instance, starting with a 1:200 site analysis before moving to 1:50 room layouts ensures a solid understanding of the overall site before focusing on the details. However, the process is not strictly linear; designers should be prepared to zoom out for context and then zoom in for specifics as needed.

While every project is unique, the following scales are commonly used in an undergraduate design project:

Site analysis - 1:1000, 1:1250

Focus on researching the site, including neighbouring buildings, the environment, and its relationship with the city or landscape.

Concept design - 1:200, 1:500

Explore how the site might be occupied through sketching, considering mass, form, and light.

Design development - 1:50, 1:100

Develop interior and exterior layouts in plan, section, and elevation with increasing detail.

Construction - 1:20, 1:10, 1:5, 1:2

Detail the materials and construction methods, showing how they will come together.

How to use a scale ruler

A scale ruler may look like a standard ruler, but it includes various standard architectural scales on its edges, making it an essential tool for accurately converting between real-life measurements and scaled drawings.

Convert real-life to scale

To use a scale ruler, first determine the scale of your drawing. For instance, if you are drawing a room at a 1:50 scale, a real-life measurement of 3m (3000mm) will be represented as 60mm on the drawing.

Align the scale ruler with the chosen scale (in this case, 1:50) and draw the line directly to 3m on the scale ruler, which will automatically be 60mm on your drawing. There’s no need for manual conversion.

Convert scale to real-life

Find the scale used in the drawing or model, typically noted in the drawing’s title block or near the image.

Use the corresponding edge of the scale ruler to measure the drawing, which will give you the real-life dimension.

Selecting a scale ruler

Decide whether you need a metric (millimetres, metres) or imperial (feet, inches) scale ruler, depending on the standard measurement system used in your country.

Ensure that the scale ruler includes the standard architectural scales you need. Different professions might use different scales, so select a ruler that covers the scales relevant to your work.

‍Representing scale in drawings

In architectural drawings, scale can be represented formally, such as through written scales or scale bars. However, scale can also be implied by including elements like people or furniture in your drawings, which help viewers intuitively understand the proportions.

Scale drawings work best as a reference tool if printed exactly the correct size, usually 100% on your printer settings. Printing drawings at slightly the wrong scale is common. At architecture school, it’s important not to make this mistake.

Scale bars

A scale bar is a visual key on a drawing that indicates the scale at which it has been created. It marks out specific lengths for easy reference. For example, on a 1:100 drawing, a scale bar might show a reference length of 10 metres.

You can measure the scale bar with a ruler to determine the length of a ‘unit,’ which you can then use as a reference to measure other parts of the drawing. For instance, if the scale bar shows 5 metres, you can use this length to estimate other dimensions in the drawing.

You can check if a drawing has been printed to scale by measuring the scale bar. If the scale bar measures correctly, the entire drawing is likely printed to the correct scale.

Written scale

When reading scale drawings, first look for the scale it has been drawn at—in this case 1:100 when printed at A3.

After identifying the written scale, use the corresponding side of your scale ruler to accurately measure and interpret the drawing.

You can measure the drawing using the correct scale as a reference.

Scale people

Incorporating people, furniture, trees, and other elements into your drawings or models can provide viewers with a clear sense of scale, even if it's not mathematically precise. Adding these elements helps to humanise the design and allows others to better understand the proportions and spatial relationships.

We recommend adding scale people to drawings while you produce them; this means you have an easy human reference.

We offer a range of architectural resources, including free scale people, which can be easily added to your drawings.

History of architectural scale

Architectural scale can be understood in various contexts, such as the relationship between different spaces or the visual impact of a tall tower on a low-rise street. However, this tutorial focuses on representational architectural scale—how we communicate design through scale drawings and models.

The Renaissance saw the use of orthogonal projections—plans, sections, and elevations—where scale became a fundamental part of the design process.

Maps could be considered the earliest form of architectural scale but often lacked accurate proportionality. Important buildings, like churches and castles, were frequently illustrated larger than other structures to signify their importance rather than their actual size.

The first known use of a true architectural scale in the UK map dates to 1545, with a plan of the town of Portsmouth. This map was drawn to a scale of 1 inch to 100 feet (1:100).

Architectural scale has remained largely consistent over the centuries. The most notable change in the 20th century was the widespread adoption of the metric system for architectural drawings, replacing imperial. The United States remains a significant exception, continuing to use the imperial system.